Best SMTP relay services in 2026

For apps and self-hosted tools that send over SMTP, Unitpost ranks first: 5,000 emails a month free, send-only SMTP passwords, and SMTP, API and campaigns on one account. Resend, Mailgun and SMTP2GO score highest on SMTP setup, Postmark keeps 45 days of activity on every plan, and Amazon SES costs least at high volume.

Updated November 2, 2026. We make Unitpost, and it is on this list. Every score has a reason and the weights are published below, so you can re-rank it for your own needs. How we scored

#	Product	Best for	Free plan	Score
1	Unitpost	apps that send over SMTP and the API	5,000 emails a month, 200 a day, no card	4.2
2	Resend	developers who want domain-limited SMTP keys	3,000 emails a month, 100 a day	4.1
3	SMTP2GO	networks that block the usual ports	1,000 emails a month, 200 a day	3.9
4	Brevo	teams that keep logs for a long time	300 emails a day	3.9
5	Postmark	transactional mail where inbox time matters	100 emails a month	3.8
6	Mailgun	per-domain SMTP credentials	100 emails a day on one domain	3.5
7	Amazon SES	high volume at the lowest price	None for SES; new AWS accounts get up to $200 in credits	3.4
8	Mailtrap	teams that already test email in Mailtrap	4,000 emails a month, 150 a day	3.4

What every SMTP relay asks you to set

Host and port: 587 with STARTTLS or 465 with implicit TLS; if a cloud host blocks both, the relay's fallback port (2525, or 2587 and 2465)
Username and password: often a fixed username with an API key as the password, so a key per app means you can revoke one app
A From address on a domain you verified with the relay, so its SPF and DKIM pass
A test send, then the relay's log, to confirm the message was accepted and delivered

The picks

#1 · 4.2 / 5

Unitpost

Best for apps that send over SMTP and the API

SMTP on 587 and 465 with send-only passwords, the same send checks as the API and MCP server, and 60 days of logs on paid plans. 5,000 emails a month free.

Pros

Every SMTP password is a send-only key you revoke on its own
SMTP, API, campaigns and inbound on one account
SMTP setup guides for 34 self-hosted apps

Cons

No 2525 port (2587 and 2465 instead)
Keys can't be limited to one domain
A short public deliverability record

Free plan: 5,000 emails a month, 200 a day, no card
Paid from: $10 a month for 20,000 emails
Priced by: Emails sent

Start free See pricing

#2 · 4.1 / 5

Resend

Best for developers who want domain-limited SMTP keys

SMTP on five ports with TLS, keys that can only send and only from one domain, and 30 days of data on every plan.

Pros

Sending-only keys limited to one domain
30 days of data, free plan included
Ports 465, 587, 2465, 2587 and 25

Cons

The free plan caps at 100 emails a day
No 2525 port

Free plan: 3,000 emails a month, 100 a day
Paid from: $20 a month for 50,000 emails
Priced by: Sends and contacts

Unitpost vs Resend Visit Resend

#3 · 3.9 / 5

SMTP2GO

Best for networks that block the usual ports

An SMTP-first relay with eight ports, unlimited SMTP users with their own rate limits, and a free plan of 1,000 emails a month.

Pros

Ports 25, 80, 443, 465, 587, 2525, 8025 and 8465
Unlimited SMTP users, each with a rate limit
A hosted MCP server and eight official libraries

Cons

1,000 emails a month free
5 days of activity on the free plan

Free plan: 1,000 emails a month, 200 a day
Paid from: $10 a month for 10,000 emails
Priced by: Emails sent

Visit SMTP2GO

#4 · 3.9 / 5

Brevo

Best for teams that keep logs for a long time

An SMTP relay inside a marketing suite, with a large free plan and transactional logs kept until you set a limit.

Pros

300 emails a day free
Logs kept indefinitely by default
A key per integration

Cons

One SMTP login per account, with no per-domain keys
Three ports only

Free plan: 300 emails a day
Paid from: $9 a month for 5,000 emails
Priced by: Emails sent

Unitpost vs Brevo Visit Brevo

#5 · 3.8 / 5

Postmark

Best for transactional mail where inbox time matters

A transactional sender with a long public inbox-placement record, SMTP tokens per message stream and 45 days of activity on every plan.

Pros

45 days of activity on every plan
SMTP tokens per message stream
A long public time-to-inbox record

Cons

100 emails a month free
No port 465

Free plan: 100 emails a month
Paid from: $15 a month for 10,000 emails
Priced by: Emails sent

Unitpost vs Postmark Visit Postmark

#6 · 3.5 / 5

Mailgun

Best for per-domain SMTP credentials

SMTP on four ports with credentials per domain, separate from API keys, and deliverability tooling on higher plans.

Pros

SMTP credentials per domain
Ports 25, 465, 587 and 2525
Validation and inbox placement tests

Cons

1 day of logs on Free and Basic
100 emails a day free

Free plan: 100 emails a day on one domain
Paid from: $15 a month for 10,000 emails
Priced by: Emails sent

Unitpost vs Mailgun Visit Mailgun

#7 · 3.4 / 5

Amazon SES

Best for high volume at the lowest price

AWS's sender, priced per email with no minimum, with SMTP credentials as IAM users. Reputation monitoring is yours to set up.

Pros

Pay per email, no monthly minimum
IAM policies on every SMTP credential
Ports 25, 465, 587, 2465 and 2587

Cons

Searching sent mail needs the Virtual Deliverability Manager
No free tier beyond AWS credits

Free plan: None for SES; new AWS accounts get up to $200 in credits
Paid from: $0.10 per 1,000 emails (new accounts start on a $0.16 plan)
Priced by: Emails sent

Visit Amazon SES

#8 · 3.4 / 5

Mailtrap

Best for teams that already test email in Mailtrap

A sending service beside Mailtrap's testing sandbox, with a free plan of 4,000 emails a month and per-domain tokens as SMTP passwords.

Pros

4,000 emails a month free
Per-domain tokens that can expire
Eight official SDKs

Cons

No port 465
3 days of logs free, 5 on Basic

Free plan: 4,000 emails a month, 150 a day
Paid from: $15 a month for 10,000 emails
Priced by: Emails sent

Visit Mailtrap

Scores side by side

Product	SMTP setup30%	Free plan20%	Deliverability20%	Logs15%	First paid step15%	Total
Unitpost	4	5	3	4	5	4.2
Resend	5	4	3	5	3	4.1
SMTP2GO	5	3	3	4	4	3.9
Brevo	3	5	3	5	4	3.9
Postmark	4	2	5	5	3	3.8
Mailgun	5	3	4	1	3	3.5
Amazon SES	4	2	3	3	5	3.4
Mailtrap	4	4	3	2	3	3.4

How we scored

This list is for developers who configure SMTP in an app, a framework's mailer, or a self-hosted tool such as GitLab, Ghost or Keycloak: a host, a port, a username and a password. What matters is which ports work behind your firewall, whether each app gets its own revocable credential, how long you can look a message up, and the free and first paid plans.

SMTP setup (30%). Ports 587 and 465 with TLS, fallback ports for networks that block them, and SMTP credentials you can limit and revoke one by one.
Free plan (20%). A permanent free plan large enough to run a small app on, with no card.
Deliverability (20%). A long public record of inbox placement, and the tooling to protect it.
Logs (15%). How long each message stays searchable on the cheapest paid plan, with delivery webhooks.
First paid step (15%). A cheap first paid plan that grows with sends.

Each product gets 1 to 5 per criterion, from its own pricing and docs pages. The total is the weighted mean, so changing a weight re-ranks the list.

Why Unitpost scored 4.2

SMTP setup: 4/5. 587 and 465 with TLS, plus 2587, 2465 and 25; each SMTP password is a send-only key revoked on its own, but not limited to one domain.
Free plan: 5/5. 5,000 emails a month free for good, 200 a day, no card.
Deliverability: 3/5. Guided SPF, DKIM and DMARC with continuous checks, but a short public record so far.
Logs: 4/5. 7 days of logs on free and 60 days on paid plans, with signed webhooks for every event.
First paid step: 5/5. $10 a month for 20,000 emails, priced by sends.

Checked November 2, 2026 against unitpost.com/pricing, unitpost.com/sms, registry.npmjs.org/unitpost.

Why Resend scored 4.1

SMTP setup: 5/5. 465, 587, 2465, 2587 and 25; sending-only keys that can be limited to one domain.
Free plan: 4/5. 3,000 emails a month free, capped at 100 a day.
Deliverability: 3/5. A shorter public record than SendGrid or Postmark.
Logs: 5/5. 30 days of data on every plan, free included.
First paid step: 3/5. Pro is $20 a month for 50,000 emails; marketing contacts are a second plan.

Checked November 2, 2026 against resend.com/pricing, resend.com/migrate, resend.com/docs/dashboard/receiving/introduction, github.com/resend/mcp-send-email, resend.com/docs/send-with-smtp, resend.com/docs/api-reference/api-keys/create-api-key, registry.npmjs.org/resend, resend.com/docs/dashboard/webhooks/retries-and-replays.

Why SMTP2GO scored 3.9

SMTP setup: 5/5. Eight ports, 2525, 8025 and 443 among them, and unlimited SMTP users, each with its own rate limit and status.
Free plan: 3/5. 1,000 emails a month free, 200 a day, no card.
Deliverability: 3/5. Shared IPs to start; a dedicated IP comes with Professional, at 100,000 emails a month.
Logs: 4/5. 5 days of searchable activity free and 30 days on paid plans, extendable to 2 years, with webhooks.
First paid step: 4/5. Starter is $10 a month for 10,000 emails, then $1 per 1,000.

Checked November 2, 2026 against smtp2go.com/pricing/, smtp2go.com/faq/, support.smtp2go.com/hc/en-gb/articles/223087627-SMTP-Settings, support.smtp2go.com/hc/en-gb/articles/13645646122777-SMTP-User-Authentication, developers.smtp2go.com/docs/official-libraries, developers.smtp2go.com/docs/view-account-activity.

Why Brevo scored 3.9

SMTP setup: 3/5. 587, 465 and 2525; one SMTP login per account, a key per integration, no per-domain scoping.
Free plan: 5/5. 300 emails a day, about 9,000 a month, on a permanent free plan.
Deliverability: 3/5. An established sender, without Postmark's public time-to-inbox record.
Logs: 5/5. Transactional logs kept indefinitely by default.
First paid step: 4/5. Starter from $9 a month, sized by email volume.

Checked November 2, 2026 against brevo.com/pricing/, developers.brevo.com/docs/mcp-protocol, help.brevo.com/hc/en-us/articles/7959631848850, help.brevo.com/hc/en-us/articles/360021533839, registry.npmjs.org/@getbrevo/brevo.

Why Postmark scored 3.8

SMTP setup: 4/5. 25, 587 and 2525 with STARTTLS but no 465; SMTP tokens per message stream.
Free plan: 2/5. 100 emails a month free, enough to test, not to run an app.
Deliverability: 5/5. A long public record of time-to-inbox, protected by separate streams.
Logs: 5/5. 45 days of activity on every plan, extendable to 365.
First paid step: 3/5. Basic is $15 a month for 10,000 emails.

Checked November 2, 2026 against postmarkapp.com/pricing, postmarkapp.com/migration-guides, postmarkapp.com/lp/mcp, postmarkapp.com/developer/user-guide/send-email-with-smtp, registry.npmjs.org/postmark, postmarkapp.com/developer/webhooks/inbound-webhook.

Why Mailgun scored 3.5

SMTP setup: 5/5. 25, 465, 587 and 2525; SMTP credentials per domain, separate from API keys.
Free plan: 3/5. A free plan of 100 emails a day on one domain, with one day of logs.
Deliverability: 4/5. Validation, inbox placement tests and dedicated IPs.
Logs: 1/5. 1 day of logs on Free and Basic, 5 on Foundation.
First paid step: 3/5. Basic from $15 a month for 10,000 emails.

Checked November 2, 2026 against mailgun.com/pricing/, mailgun.com/resources/guides/migrating-from-sendgrid-to-mailgun-email-api/, documentation.mailgun.com/docs/mailgun/mcp, documentation.mailgun.com/docs/mailgun/user-manual/sending-messages/send-smtp, registry.npmjs.org/mailgun.js, documentation.mailgun.com/docs/mailgun/user-manual/receive-forward-store/receive-http.

Why Amazon SES scored 3.4

SMTP setup: 4/5. TLS on 465 and 2465, STARTTLS on 25, 587 and 2587; credentials are IAM users with their own send policy, per region.
Free plan: 2/5. No SES free tier; new AWS accounts get up to $200 in credits.
Deliverability: 3/5. Good infrastructure, but reputation monitoring is your job.
Logs: 3/5. Searching sent messages, 30 days back, needs the Virtual Deliverability Manager.
First paid step: 5/5. Pay per email from $0.10 per 1,000, with no monthly minimum.

Checked November 2, 2026 against aws.amazon.com/ses/pricing/, docs.aws.amazon.com/ses/latest/dg/smtp-connect.html, docs.aws.amazon.com/ses/latest/dg/smtp-credentials.html, docs.aws.amazon.com/ses/latest/dg/vdm-dashboard.html, registry.npmjs.org/@aws-sdk/client-sesv2, docs.aws.amazon.com/ses/latest/dg/receiving-email-notifications-contents.html.

Why Mailtrap scored 3.4

SMTP setup: 4/5. 587, 25 and 2525 with STARTTLS but no 465; per-domain tokens as passwords, with expiry and reset.
Free plan: 4/5. 4,000 emails a month free, 150 a day, no card; the quota is shared with inbound.
Deliverability: 3/5. A dedicated IP from the Business plan, at $85 a month for 100,000 emails.
Logs: 2/5. Email logs kept 3 days on Free and 5 on Basic.
First paid step: 3/5. Basic is $15 a month for 10,000 emails.

Checked November 2, 2026 against mailtrap.io/pricing/, docs.mailtrap.io/developers, docs.mailtrap.io/email-api-smtp/setup/smtp-integration, mailtrap.io/mandrill-migration/, mailtrap.io/email-mcp-server/.

Frequently asked questions

Which SMTP port should I use?

587 with STARTTLS, or 465 with implicit TLS. Cloud servers often block port 25 for outbound mail. If 587 and 465 are blocked too, use the relay's fallback port: 2525 on most relays here, 2587 or 2465 on Unitpost, Resend and Amazon SES.

What happened to SparkPost?

sparkpost.com now redirects to Bird. Bird points new integrations to Bird Email, which has its own API, SMTP on ports 465, 587 and 2525, and a free plan of 1,000 emails a month at 50 a day.

Is SMTP worse than an email API?

Not for delivery: on most relays both reach the same sending pipeline. SMTP needs no code beyond a mailer's settings, which suits self-hosted tools; an API gives you idempotency keys, batch sends and structured errors. On Unitpost both pass the same send checks.

Go deeper: SMTP setup guides · SMTP reply codes · Free email APIs · SendGrid alternatives

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