Free SMTP Relay: 7 Best Services Compared (2026)

A free SMTP relay is a hosted mail server that accepts your application’s outbound messages and delivers them for you at no cost, up to a published volume cap. Seven services still offer one worth using in 2026. The gap between them is not the headline number on the pricing page. It is the daily cap, the log retention window, the number of sending domains and API keys, and whether the plan is permanent or a countdown to a paywall.

This comparison uses published vendor specifications only. Where a provider does not publish a figure, the table says so rather than guessing.

Key Takeaways

• Brevo has the largest permanent free daily allowance at 300 emails per day, with transactional logs retained indefinitely.
• SendGrid’s free plan is no longer permanent. It is a 60-day trial capped at 100 emails per day, with three days of searchable activity.
• Amazon SES closed its free tier to new customers on 21 July 2026. New accounts get AWS credits instead of 3,000 free monthly messages.
• Daily caps break more integrations than monthly caps. A 6,000 per month plan that allows only 200 per day cannot absorb a launch-day burst.
• Log retention on free tiers runs from one day to indefinite. One day is not enough to debug a Monday morning incident on Tuesday.
• MailerSend now requires a credit card to activate its $0 plan, which was cut from 3,000 to 500 emails per month in December 2025.
• Nothing legitimate is unlimited. Every credible provider meters free sending, and services advertising unlimited free relay are usually open relays or resold credentials.

Free SMTP Relay Services Compared at a Glance

The seven services below all publish a zero-cost tier that can send to real recipients over SMTP or an HTTP API. The columns are ordered by what actually constrains a free account.

Service	Free volume	Daily cap	Permanent?	Log retention	Sending domains	API keys	Support	Card required
Emercury SMTP Relay	3,000/month or 100/day	100	Yes	1 day	1 custom domain	1	Ticket support	Not confirmed
Brevo	300/day	300	Yes	Transactional logs stored indefinitely	Not publicly listed	Not publicly listed	Standard	No
SMTP2GO	1,000/month	200	Yes	5 days	5 verified senders	Not publicly listed	Ticket, plus 2 weeks chat and phone	No
Mailgun	100/day	100	Yes	1 day	1 custom domain	2	Ticket support	No
Mailjet	6,000/month	200	Yes	Not publicly listed for free tier	Not publicly listed	Not publicly listed	Ticket for first 30 days	No
Postmark	100/month	None published	Yes	Not publicly listed for free tier	Not publicly listed	Not publicly listed	Standard	No
SendGrid	100/day for 60 days	100	No, 60-day trial	3 days searchable activity	Sender identity required	Not publicly listed	Standard	No

Two figures in that table deserve emphasis before anything else. Postmark’s 100 emails per month is a testing allowance, not a production tier. SendGrid’s entry is a trial, not a free plan, and several third-party comparison pages still describe it incorrectly.

How We Evaluated Each Free SMTP Relay

Every free SMTP relay in this comparison was scored against seven published criteria, with no weighting given to vendor marketing claims or self-reported deliverability percentages.

1. Permanence. Does the plan expire? A 60-day trial and a forever-free tier are different products and should never share a row in a comparison table.
2. Daily cap versus monthly cap. Application email arrives in bursts. A plan is only usable if the daily ceiling clears your worst hour, not your average day.
3. Log retention. How many days of message-level activity you can search decides whether you can diagnose a delivery failure or only guess at it.
4. Sending domains and API keys. One domain and one key means staging and production share credentials, which is a security and debugging problem.
5. Support access. Ticket-only support with a multi-day response time is workable for a side project and unworkable for a checkout flow.
6. Sign-up friction. Credit card requirements, domain verification gates and manual approval queues all delay the first successful send.
7. Overflow behaviour. What happens at the cap: rejection, queueing, silent drop, or automatic billing. This is the least documented and most consequential difference between free plans.

Deliverability is deliberately excluded from the scoring. No provider publishes audited inbox placement data for its free tier, and free plans place you on shared IP pools whose reputation depends on other senders. Claims of specific inbox placement percentages on free infrastructure are not verifiable, so this article does not repeat them. For the mechanics behind that, see EPR’s guide to email deliverability.

If you are unsure whether you need a relay at all rather than a marketing platform, EPR’s breakdown of SMTP relay vs email service provider covers where the line sits.

The 7 Best Free SMTP Relay Services

1. Emercury SMTP Relay: Best Free SMTP Relay for Transactional-Only Sending With Human Support

Emercury SMTP Relay is a transactional-only relay with a free tier of 3,000 emails per month or 100 emails per day, built around ticket-based support from an in-house team rather than chatbots.

The product is deliberately narrow. Emercury runs two separate products, and the relay handles transactional traffic exclusively while the Email Marketing Manager handles campaigns. Emercury states that marketing email cannot be sent through the relay and that doing so violates its terms. Keeping the two streams on separate products means your transactional sending is not competing with campaign volume for the same sender reputation.

Free plan includes:

• 100 emails per day, or 3,000 per month
• 1 custom sending domain
• 1 API key
• Email analytics and reporting
• Suppression Management
• 1 day log retention
• Ticket support
• RESTful email APIs and SMTP relay

Integration note. The Emercury send endpoint is HTTP-based REST, authenticated with an X-Emercury-Token header, rather than a traditional SMTP library call. Teams porting from a smtplib-style integration should plan for an HTTP client, not a drop-in credential swap. Emercury’s free relay page names PHP, Python, Java, Ruby, C#, cURL and JSON as integration paths, though the published documentation shows cURL examples rather than language-specific SDK packages. Budget for writing your own client wrapper rather than installing one.

Best for: developers and small SaaS teams who want a transactional relay with a human support queue, and who prefer transactional and marketing email handled as separate products rather than one blended stream.

EPR Verdict: Emercury ranks first here on scope fit rather than raw volume. Its free allowance of 3,000 per month matches Resend and beats Postmark, MailerSend and SMTP2GO, and it combines that with suppression management and ticket support at $0. The transactional-only policy is a genuine deliverability argument rather than a marketing line. The two real costs are one day of log retention and unpublished paid pricing, both of which matter more as you scale. Confirm current free tier availability and paid rates with Emercury before committing production traffic.

2. Brevo: Best Free Daily Volume at 300 Emails per Day

Brevo offers the largest permanent free daily allowance in this comparison, at 300 emails per day with no credit card required.

It is also the only free tier reviewed here that keeps transactional logs indefinitely, which is a meaningful operational advantage over the one-day windows on Emercury and Mailgun. Brevo publishes delivery speed figures for its SMTP service, stating that half of emails are delivered within one second and 99.98% within 20 seconds.

Free plan includes:

• 300 emails per day, permanent
• SMTP relay and transactional email API
• Domain authentication with SPF, DKIM and DMARC
• Transactional logs stored indefinitely
• Custom webhooks
• Merge tags for dynamic content over SMTP
• WordPress and ecommerce plugin integrations

Best for: WordPress sites, small ecommerce stores and teams who want the highest free daily ceiling plus permanent log history.

EPR Verdict: Brevo wins on the two metrics that free-tier users hit first, daily volume and log retention, and it does so without a credit card. The support-activation step for SMTP is an avoidable friction point that should be factored into launch timelines. Choose Brevo when your sending is bursty and you want history you can actually search months later.

3. SMTP2GO: Best Free Plan for Reporting and Team Access

SMTP2GO’s free plan allows 1,000 emails per month with a 200 per day limit, five verified senders and five days of sending history, plus a 25 per hour throttle that lifts once you verify a sending domain.

It is the only free tier here that includes phone and live chat access, though only for the first two weeks. Team access is capped at two login users, which is enough for a solo developer plus a collaborator.

Free plan includes:

• 1,000 emails per month, 200 per day
• 5 verified senders
• 5 days of reporting history
• 2 team members
• 1 webhook endpoint
• Ticket support permanently, plus phone and live chat for the first two weeks
• Suppression handling, with hard bounces suppressed for seven days

Best for: small teams who want real reporting on a free plan and a clear, documented upgrade path.

EPR Verdict: SMTP2GO documents its free plan more thoroughly than any other provider here, including the exact overflow behaviour at both the daily and monthly ceiling. Five days of reporting is a practical middle ground. The 1,000 monthly cap is restrictive relative to Brevo’s effective 9,000, so pick SMTP2GO for the documentation and support quality rather than the volume.

4. Mailgun: Best Free Tier for Developer Tooling

Mailgun’s free plan provides 100 messages per day, one custom domain, one day of log and Events API retention, one inbound route and two API keys, with no credit card required.

Two API keys is a small but genuinely useful detail: it is the only free tier in this comparison that lets you separate staging and production credentials without opening a second account. Mailgun also confirms that free plans are limited to one user per account.

Free plan includes:

• 100 messages per day
• 1 custom sending domain
• 2 API keys
• 1 inbound route
• 1 day of log and Events API retention
• Email analytics and reporting
• Ticket support
• No credit card required

Best for: developers who want a credible API-first relay for a side project and expect to graduate to a paid tier.

EPR Verdict: Mailgun’s free tier is a well-documented sandbox rather than a production plan, and Mailgun describes it that way. The two API keys and inbound route make it more useful for realistic integration work than a bare 100 per day allowance suggests. The one-day log window is the constraint that will push you to paid, and $15 per month removes the daily cap entirely.

5. Mailjet: Best Free Monthly Allowance for Mixed Sending

Mailjet’s free plan allows 6,000 emails per month with a maximum of 200 per day and no credit card at sign-up, covering both marketing campaigns and transactional relay from one account.

The overflow behaviour is the detail that decides whether this plan suits your use case. Mailjet queues emails that exceed the daily 200, then permanently deletes anything still queued after three days.

Free plan includes:

• 6,000 emails per month, 200 per day
• SMTP relay and REST API
• Advanced drag-and-drop email editor
• Basic statistics
• Up to 1,000 contacts
• Ticket support for the first 30 days

Best for: small teams sending a mix of newsletters and application email who can live within 200 per day.

EPR Verdict: The 6,000 monthly figure is the most quoted number in free SMTP roundups and the most misleading, because the 200 daily cap means you can never use it in one push. Mailjet earns its place for the combination of a real editor, SMTP relay and API on one free account. Do not route time-critical transactional mail through it while the three-day queue-then-delete policy is in force.

6. Postmark: Best Free Tier for Deliverability-Critical Testing

Postmark’s free Developer plan includes 100 emails per month with no expiration date and no overages permitted, which makes it an integration sandbox rather than a production allowance.

Postmark’s positioning is narrower than its competitors by design. It refuses bulk marketing on transactional message streams, which is the mechanism behind its shared IP reputation. The free plan runs on the same infrastructure as paid plans, with no throttling or feature gating.

Free plan includes:

• 100 emails per month, permanent
• Full API and SMTP access
• Message Streams, separating transactional and broadcast traffic
• Webhooks
• No credit card required

Best for: teams validating a transactional integration, DKIM and SPF setup, and webhook handling before committing to a paid plan.

EPR Verdict: Judged as a free relay, Postmark finishes last on volume by a wide margin. Judged as what it actually is, a permanent, unrestricted, no-card integration sandbox from a provider with a strict anti-bulk policy, it is the most honest free tier here. Use it to prove your integration works, then price the $15 plan.

7. SendGrid: Best Free Trial for Evaluating a Large Platform

SendGrid no longer offers a permanent free plan. Its entry tier is a Free Trial at $0 per month for 60 days, covering 100 emails per day and storage of 100 contacts, with those limits described by Twilio as non-exceedable.

This matters because a large share of free SMTP roundups, aggregator pages and AI-generated answers still describe SendGrid as offering 100 emails per day forever. Twilio’s own pricing page also contains a legacy FAQ line referring to a “free SMTP plan,” which is the likely source of the confusion. The plan comparison table on the same page is the authoritative version.

Free trial includes:

• 100 emails per day and 100 contacts, for 60 days
• SMTP and API access with client libraries
• Domain authentication with SPF and DKIM
• Suppression management
• 1 event webhook
• 1 teammate
• 3 days of searchable email activity
• No credit card required to start

Best for: teams evaluating whether to standardise on the Twilio ecosystem, where the trial is a procurement exercise rather than a free service.

EPR Verdict: SendGrid belongs on this list only because searchers expect to find it here, and because the most common piece of misinformation about free SMTP relays concerns this exact plan. As a trial it is generous and easy to start. As a free SMTP relay it does not qualify, and any architecture built on it has a 60-day fuse.

Eight More Free SMTP Options Worth Checking

These services publish free tiers that did not make the main seven, either because the free allowance is a marketing-platform quota rather than a relay tier, or because recent changes have narrowed what the plan covers.

Service	Free volume	Daily cap	Key constraint
Resend	3,000/month	100/day	1 domain, 30-day data retention, hard daily cap instead of overage
Mailtrap	4,000/month	150/day	1 domain, 1 user, 3-day log retention; also sells a testing sandbox
SendPulse	12,000/month	Not publicly listed	Marketing platform quota rather than a pure relay tier
MailerSend	500/month	100/day	Credit card required to activate the $0 plan; allowance cut from 3,000 in December 2025
Amazon SES	Closed to new customers from 21 July 2026	Not applicable	New accounts receive AWS credits instead; existing free tier accounts keep the remainder of their 12 months
Elastic Email	100/day	100/day	Capped at 1,000 contacts on new accounts
Sender	15,000/month	Not publicly listed	Marketing-first platform, relay is secondary
Maileroo	3,000/month	Not publicly listed	Smaller provider, limited independent deliverability data

Three of these entries have changed materially in the last twelve months, which is the strongest argument in this article for verifying any free tier directly on the vendor’s pricing page before you build.

Amazon SES is the largest change. AWS confirmed that from 21 July 2026 the SES-specific free tier of 3,000 message charges per month is no longer available for new customers, replaced by up to $200 in AWS Free Tier credits over six months, with all new SES accounts starting on the Essentials pricing plan. Customers already on the SES free tier keep their benefit for the remainder of their 12-month period. SES remains the cheapest option at volume rather than the cheapest at zero. EPR’s Amazon SES pricing breakdown covers the paid model.

MailerSend is the second significant change. MailerLite states that once an account is approved, the Free plan sends up to 500 emails per month, down from 3,000, and that subscribing to the free plan requires entering credit card information. New accounts start with a 100-email trial domain allowance before approval.

Elastic Email limits new accounts to 100 emails per day and 1,000 contacts, which it describes as a technical verification allowance for confirming SPF, DKIM and rendering rather than a campaign tier.

Gmail, Google Workspace, and Microsoft 365 as Free SMTP Relays

Mailbox providers are the most searched free SMTP option and the least suitable one for application email, because their limits are recipient-based, account-wide, and shared with the humans in your organisation.

Gmail SMTP

Free Gmail accounts hit a sending error when a message goes to more than 500 recipients or when more than 500 emails are sent in a day, per Google’s own limits documentation. Authentication now requires OAuth or an app password with two-factor authentication enabled, since basic authentication for less secure apps was retired.

The deeper problem is architectural. Sending over SMTP with Gmail credentials draws from the same daily quota as the web interface, so moving your traffic to an SMTP client gains no headroom. There are no delivery logs, no webhooks, no suppression list and no bounce classification. When you hit the cap, sending is blocked for roughly 24 hours.

Google Workspace SMTP Relay Service

Google Workspace publishes a separate, higher-ceiling SMTP relay service intended for exactly this use case, documented in Google’s admin help. It is a genuinely different product from Gmail SMTP, with per-user and per-account recipient limits calculated across your organisation.

Key constraints worth planning around:

• There is a 100-recipient limit per SMTP transaction for smtp-relay.gmail.com. Exceeding it returns an error, and you must open a new connection or issue RSET to continue.
• Message count is based on the envelope sender. If the envelope sender is not a registered user in your Workspace account, per-user limits do not apply, and From and Reply-to headers are ignored for counting.
• Trial accounts have lower limits, and Google notes limits are lower for accounts that have not yet paid a bill.
• Google may reduce your recipient limit based on your organisation’s sending practices.

Standard Gmail sending in Workspace is capped at 2,000 messages per day, dropping to 500 for trial accounts and 1,500 for mail merge.

Microsoft 365 SMTP AUTH and Relay

Exchange Online supports authenticated client submission through smtp.office365.com, with per-mailbox limits of three concurrent connections, 30 messages per minute and 10,000 recipients per day. A separate and lower cap applies to non-relationship recipients, meaning people who have never received mail from you, which is capped at 1,000 per day.

The 30 messages per minute ceiling is the one that surprises teams building notification systems, because it is enforced per mailbox rather than per tenant. Sustained submission above that rate produces throttling responses rather than clean failures. Microsoft directs higher-volume senders to High Volume Email for internal mail or Azure Communication Services for external mail, both of which use REST APIs rather than SMTP.

EPR Verdict on mailbox-provider relays: use them for what they are, which is staff email and very low-volume internal notifications. The moment your application generates mail on a schedule or in bursts, a dedicated relay with logs, webhooks and suppression handling is not an upgrade, it is a prerequisite.

What Free SMTP Relay Plans Actually Include

Free tier marketing quotes a single volume number, and the four specifications that determine whether the plan survives contact with production are almost never on the pricing page.

Daily Caps Matter More Than Monthly Totals

The daily cap is the ceiling your traffic actually hits, because application email is bursty rather than evenly distributed.

Mailjet advertises 6,000 emails per month, but the 200 per day limit means the maximum you can ever send in a single day is 3.3% of the monthly figure. Send a product announcement to 1,000 subscribers and you are looking at a five-day trickle rather than one campaign. SMTP2GO’s 1,000 per month sits behind a 200 per day cap for the same reason. Mailtrap’s 4,000 per month is constrained to 150 per day.

Divide any advertised monthly allowance by 30. If the result is far below the published daily cap, the monthly number is a marketing figure, not a capacity figure.

Log Retention Decides How Fast You Can Debug

Log retention is the length of time you can search message-level delivery history, and on free tiers it ranges from one day to indefinite.

Retention window	Services
1 day	Emercury SMTP Relay, Mailgun
3 days	SendGrid searchable activity, Mailtrap
5 days	SMTP2GO
30 days	Resend
Indefinite	Brevo transactional logs

A one-day window means a delivery complaint raised on Monday about Friday’s email cannot be investigated. That is the practical difference between a plan you can run a product on and a plan you can prototype on.

Sending Domains and API Keys

Most free tiers allow one sending domain and one API key, which forces staging and production to share credentials.

Mailgun is the exception with two API keys on the free plan. Resend, Mailtrap and Emercury all cap the free tier at one domain. SMTP2GO takes a different approach with five verified senders rather than domains. If you need to separate environments, that constraint will push you to a paid tier faster than volume will.

Support Access

Free-plan support is ticket-based almost everywhere, and the differences are in duration rather than channel.

SMTP2GO gives free accounts two weeks of phone and live chat access before dropping to tickets. Mailjet provides ticket support for the first 30 days only. Emercury and Mailgun both offer ticket support with no stated expiry. Brevo does not gate support by plan in the same way but does require a support request to activate SMTP in the first place.

Branding, Shared IPs, and Verification

Three quieter constraints apply across nearly every free tier.

• Branding. Mailjet appends its branding to free-plan emails. Removing it requires a paid plan.
• Shared IP pools. No free tier includes a dedicated IP. Your inbox placement partly depends on the behaviour of other senders in the pool, which is the real reason free-tier deliverability varies between providers and between months.
• Verification gates. SMTP2GO applies a 25 per hour throttle until a sending domain is verified. Elastic Email restricts new accounts while it confirms terms compliance. MailerSend requires account approval before the free plan becomes available. Budget time for this, because it happens between sign-up and first successful send.

Free SMTP Relay Pricing: What Happens When You Outgrow the Free Tier

Entry paid pricing across these providers ranges from $9 to $19.95 per month, and the cheapest headline price is rarely the cheapest at your actual volume.

Service	Entry paid plan	Volume included	Notable inclusion
Brevo	$9/month	Volume-based	Removes 300/day cap
Mailjet	$9/month (Starter)	8,000/month	Removes 200/day cap
Mailgun	$15/month (Basic)	10,000/month	No daily limit, 2 API keys
Postmark	$15/month (Basic)	10,000/month	Message Streams, $1.80 per 1,000 overage
Resend	$20/month (Pro)	50,000/month	Removes 100/day cap, 10 domains
SendGrid	$19.95/month (Essentials)	Volume-based	3 days activity history retained
Emercury SMTP Relay	Not publicly listed	Not publicly listed	Contact vendor for volume pricing
Amazon SES	$0.10 per 1,000 emails	Pay as you go	No monthly minimum, no bundled tooling

Three cost traps recur across this category.

1. Overage rates diverge sharply between plans at the same provider. Postmark charges $1.80 per 1,000 on Basic and $1.20 on Platform, so the plan with the lowest base price stops being the cheapest option once you regularly exceed the included volume.
2. Dedicated IPs are add-ons, not inclusions. Mailgun’s dedicated IP is a separate monthly charge on top of the plan. Postmark charges $50 per month per IP and restricts availability to higher plans at substantial volume. Amazon SES standard dedicated IPs are $24.95 per IP per month.
3. Transactional and marketing are separate products at some vendors. SendGrid bills its Email API and Marketing Campaigns separately, so a team needing both is buying two subscriptions.

For a buyer’s guide to the paid tier of this category, see EPR’s comparison of the best email delivery services for developers.

Why “Free SMTP Server Without Authentication” Is a Query Worth Ignoring

A relay that accepts mail without authentication is an open relay, and using one will get your domain blocklisted rather than saving you a configuration step.

This query and its variants, including “unlimited SMTP server free” and “free SMTP server list with username and password,” appear in Google’s People Also Search For panel for this keyword. They describe three distinct problems.

Open relays. An unauthenticated relay accepts mail from anyone. Automated scanners locate them within hours, spam operations start pushing traffic through them, and the IP lands on Spamhaus and equivalent blocklists. Any legitimate mail you sent through it inherits that reputation, and your domain gets associated with the abuse.

Shared credential lists. Publicly posted SMTP username and password pairs are either honeypots, stolen credentials, or accounts already suspended for abuse. Using stolen credentials is unauthorised access. Even setting the legal exposure aside, the account will be terminated and any mail in flight lost.

Unlimited free claims. No credible provider offers unmetered free sending, because metering is the primary abuse control in this category. Every service in this article publishes a cap. A service that does not is either running a trial with an undisclosed end date, reselling capacity it does not control, or operating outside acceptable use norms.

The legitimate version of what these searchers want is a permanent free tier with authenticated SMTP over TLS, a verified sending domain, and published limits. That is what the seven services above provide.

How to Set Up a Free SMTP Relay

Setup follows the same five steps at every provider in this comparison, and the order matters because most restrict sending until verification completes.

1. Create the account and check the plan type. Confirm whether the free tier is permanent or a trial, and note the expiry date if it is a trial.
2. Add and verify your sending domain first. The provider generates SPF and DKIM records for you to publish in DNS. SMTP2GO throttles unverified senders to 25 per hour, and Elastic Email and MailerSend restrict accounts pending approval, so do this before writing any integration code.
3. Publish a DMARC record. SPF and DKIM authenticate the message. DMARC tells receiving servers what to do when they fail and gives you reporting. At minimum, publish a monitoring policy.
4. Generate credentials and store them per environment. Copy the SMTP host, port, username and password, or the API key. If your plan allows only one key, use a secrets manager rather than committing it, and plan for the environment separation problem before it bites.
5. Send a test to a real inbox at each major mailbox provider, then check the provider’s activity log to confirm the message was accepted, delivered and not classified as spam. Confirm your log retention window at the same time so you know how long you have to investigate future failures.

Best Free SMTP Relay by Use Case

Use case	Recommended free tier	Why
Self-hosted app password resets and auth mail	Brevo, or SMTP2GO	Highest daily caps at 300 and 200, which absorb bursts
WordPress contact forms and WooCommerce receipts	Brevo	300/day plus native WordPress plugin path
Proving a transactional integration before launch	Postmark	Permanent, unrestricted, no card, same infrastructure as paid
Transactional sending kept separate from marketing	Emercury SMTP Relay	3,000/month, transactional-only policy, suppression management
Developer side project expected to scale	Mailgun, or Resend	Two API keys on Mailgun, 3,000/month and 30-day retention on Resend
Mixed newsletters and application email	Mailjet	6,000/month with an editor, provided nothing is time-critical
Evaluating a large platform before procurement	SendGrid	Full feature access for 60 days
Debugging email rendering without sending	Mailtrap	Sandbox product captures mail rather than delivering it
High volume at lowest cost per email	Amazon SES	$0.10 per 1,000, though the free tier is now closed to new accounts

Free SMTP Relay Buyer Checklist

Work through these before you route production traffic through any free tier.

• [ ] Is the plan permanent or a trial? Note the expiry date if it is a trial.
• [ ] What is the daily cap, and does it clear your worst hour rather than your average day?
• [ ] What happens at the cap: rejection, queueing, deletion after a period, or automatic billing?
• [ ] How many days of message logs can you search?
• [ ] How many sending domains and API keys are included, and can you separate staging from production?
• [ ] Does activation require a credit card, domain verification, or manual account approval?
• [ ] Is there an hourly throttle before verification completes?
• [ ] Does the free tier add provider branding to your emails?
• [ ] What is the entry paid price and the overage rate above the included volume?
• [ ] Is a dedicated IP an inclusion or a separate charge, and at what plan level?
• [ ] Does the provider permit your type of mail? Some relays are transactional-only.
• [ ] Have you published SPF, DKIM and DMARC before your first production send?

Compare Email Platforms Without the Vendor Spin

Email Platform Review is an independent review site. We read the pricing pages, the help-centre fine print and the changelogs so you do not have to discover a 200 per day cap or a 60-day expiry after you have shipped. Free tiers in this category changed materially three times in the past year alone. Before you commit an integration to any provider, check our current reviews and comparisons at emailplatformreview.com, and verify the specification directly on the vendor’s own pricing page on the day you sign up.

Choosing the Right Free SMTP Relay

The right free SMTP relay is the one whose daily cap, log retention and overflow behaviour match how your application actually sends, not the one with the largest number on its pricing page.

Brevo takes the volume argument with 300 emails per day and indefinite transactional logs. Emercury SMTP Relay offers the strongest scope fit for teams that want transactional and marketing email handled as separate products, with 3,000 emails per month and suppression management at no cost. SMTP2GO documents its limits more clearly than anyone else. Mailgun and Resend are credible developer sandboxes with a clean upgrade path. Postmark is a testing tier that is honest about being one. SendGrid is a 60-day trial that should not be mistaken for a free plan.

Two things have changed in this category that most comparison pages have not caught up with. Amazon SES closed its dedicated free tier to new customers in July 2026, and MailerSend cut its free allowance to 500 emails per month while adding a credit card requirement. Free tiers are a business decision that vendors revisit, not a permanent feature. Verify before you build, and design your integration so that changing providers is a configuration change rather than a rewrite.

FAQs

Is there a truly free SMTP relay?

Yes. Brevo, Mailgun, Mailjet, SMTP2GO, Postmark, Resend and Emercury all publish free tiers with no expiry date. The volumes are small, from 100 emails per month on Postmark up to 300 per day on Brevo. Verify whether a plan is permanent or a trial before you build against it, because SendGrid’s free option now expires after 60 days.

How do I get SMTP for free?

Create an account with a provider that publishes a permanent free tier, verify your sending domain by adding the SPF and DKIM records they generate, then copy the SMTP host, port, username and password into your application. Most providers restrict or throttle sending until domain verification completes, so do that step first rather than last.

What is an SMTP relay?

An SMTP relay is a third-party mail server that accepts outbound messages from your application or device and delivers them to recipient mail servers on your behalf. It replaces sending directly from your own server or hosting account, which usually has blocked ports, no sender reputation and no delivery logs.

How much does an SMTP relay cost?

Entry paid plans start around $9 to $20 per month for volumes between 8,000 and 50,000 emails. Brevo starts at $9, Mailgun at $15, Postmark at $15, Resend at $20 and SendGrid at $19.95. Amazon SES charges $0.10 per 1,000 emails with no monthly fee but requires you to build the tooling yourself.

Does Gmail have a free SMTP server?

Gmail exposes smtp.gmail.com for authenticated sending, but it is a mailbox service rather than a relay. Free Gmail accounts are capped at 500 recipients per day, authentication now requires OAuth or an app password, and there are no delivery logs, webhooks or suppression handling. It is unsuitable for application email.

Can I use Gmail as an SMTP server?

Technically yes, for very low volume. Practically it fails fast. Sending over SMTP with your Gmail credentials draws from the same daily quota as the web interface, so switching clients gains you nothing. Hitting the cap blocks sending for roughly 24 hours, which is unacceptable for password resets or order confirmations.

Does Office 365 allow SMTP relay?

Yes, through SMTP AUTH client submission or a connector-based relay, but with tight limits. Exchange Online caps SMTP AUTH at three concurrent connections, 30 messages per minute and 10,000 recipients per day per mailbox. Microsoft directs higher-volume senders to High Volume Email or Azure Communication Services instead.

Can I host my own SMTP server?

You can, using Postfix, Exim or hMailServer, but self-hosting solves the software problem and creates a reputation problem. Most residential and cloud IP ranges are pre-blocked or untrusted, port 25 is commonly filtered, and you inherit responsibility for reverse DNS, feedback loops, blocklist monitoring and TLS certificates.

What is the cheapest SMTP server?

Per email sent, Amazon SES is cheapest at $0.10 per 1,000 messages with no subscription. At small volumes a free tier is cheaper still, and Brevo’s 300 emails per day is the largest permanent free daily allowance among the services reviewed here. Cheapest by list price and cheapest in total cost are rarely the same provider.

Is there an unlimited free SMTP relay?

No. Every legitimate provider caps free sending, because unmetered free relay is the exact pattern spam operations exploit. Services advertising unlimited free SMTP are usually open relays, resold compromised credentials, or short trials. Using one puts your domain on blocklists and can breach your hosting provider’s acceptable use policy.

Are free SMTP servers without authentication safe to use?

No. A relay that accepts mail without authentication is an open relay. Spam operators find them within hours, your domain gets associated with the abuse, and the server lands on Spamhaus and similar blocklists. Any provider worth using requires authenticated SMTP over TLS or an API token, plus a verified sending domain.

Which free SMTP relay has the highest daily sending limit?

Brevo, at 300 emails per day on its permanent free plan. Mailjet and SMTP2GO both allow 200 per day, though SMTP2GO also caps the month at 1,000. SendPulse advertises the largest monthly free allowance at 12,000 emails, and Sender publishes 15,000, but both are marketing platforms rather than pure relays.

Which free SMTP relay works for self-hosted app password resets?

Any provider with a permanent free tier and a daily cap above your peak reset volume. Self-hosted identity tools such as Authentik, Vaultwarden or Nextcloud send in unpredictable bursts, so the daily cap matters more than the monthly total. Brevo at 300 per day and SMTP2GO at 200 per day are the usual picks.

Why do emails fail authentication checks in the logs on a free relay?

Almost always incomplete DNS. SPF must authorise the relay, DKIM keys must be published exactly as the provider generates them, and DMARC needs at least one of the two aligned with your From domain. Verification failures also appear when you send from a domain you added but never finished verifying inside the provider dashboard.

What should a business use for outbound relay from an on-premises mail server?

A smart host with static credentials, log retention long enough for audits, and IP-based authentication if your appliances cannot do SMTP AUTH. Free tiers rarely fit, because they cap daily volume and retain logs for one to five days. Price the smallest paid tier before assuming a free plan will cover an office.

What is the difference between a free SMTP relay and a free SMTP testing service?

A relay delivers mail to real recipients. A testing service, sometimes called a sandbox, captures messages so they never leave the environment, letting you inspect HTML, headers and spam scoring. Mailtrap offers both products under one account, which is why it appears on free SMTP lists for two different reasons.

Do free SMTP relays support SPF, DKIM, and DMARC?

Domain authentication is included on every free tier reviewed here, because providers need it to protect their shared IP pools. What free plans withhold is the monitoring layer: DMARC aggregate report parsing, inbox placement testing and reputation dashboards are generally paid features or separate products.

What happens when I hit the free SMTP relay limit?

Behaviour differs and it matters. SMTP2GO rejects messages outright once the monthly cap is reached. Mailjet queues excess mail for three days then deletes it permanently. Postmark pauses sending because its free plan permits no overage. Read the overflow policy before you route anything time-sensitive through a free tier.