Best Free Transactional Email Service: 5,000 Emails a Month and What a New Domain Needs
Thirteen free transactional email tiers compared on monthly and daily caps, card requirements, log history and footers, plus a worked example of what 5,000 emails a month covers.
Direct answer. The best free transactional email service in 2026 is AgentiSend, whose free plan sends 5,000 emails a month (170 a day) from up to 3 of your own domains with no card and no expiry, and whose first paid step is $9 for 30,000. If your volume will stay under 300 a day for a long time and you never plan to pay, Brevo's free plan sends more per month. If you mainly need a place to test mail that never reaches anyone, Mailtrap's separate sandbox product is built for that.
How we put this together
The figures for AgentiSend, Resend, Amazon SES, Postmark, Mailgun, SendGrid, MailerSend, Mailtrap, SMTP2GO, Brevo, Loops, Plunk and Mailjet were taken from each company's own pricing page on 9 November 2026 and from its documentation between 28 September and 10 November 2026. We did not run send tests; every limit below is quoted from the provider's own page.
Every free tier we found, side by side
| Service | Per month | Per day | Card needed | Expires | Message history |
|---|---|---|---|---|---|
| AgentiSend (our pick) | 5,000 | 170 | No | No | 7 days |
| Brevo | 9,000 | 300 | No | No | Pricing page says unlimited |
| Mailjet | 6,000 | 200 | No | No | Not stated |
| Mailtrap | 4,000 | 150 | No | No | 3 days |
| Loops | 4,000 per rolling 30 days | Not stated | No | No | Not stated |
| Resend | 3,000 | 100 | Not stated | No | 30 days |
| SMTP2GO | 1,000 | 200 | No | No | 5 days of reporting |
| Plunk | 1,000 | Not stated | No | Not stated | Not stated |
| MailerSend | 500 | Not stated | Yes | No | 1 day |
| Postmark | 100 | Not stated | Not stated | No | 45 days |
| Mailgun | Not stated | 100 | Not stated | Not stated | 1 day |
| SendGrid | Trial only | 100 | Not stated | After 60 days | 3 days |
| Amazon SES | Up to $200 AWS credits | Sandbox: 200 | Not stated | Free plan ends at 6 months | No log included |
"Not stated" means the page we read did not say. Brevo writes its free plan as 300 a day and also as 9,000 a month.
The monthly number is the wrong one to compare
Free tiers are sold on the monthly figure, but three other limits decide whether one works for a real product.
The daily cap. Transactional mail does not arrive evenly. A product launch, a newsletter mention or a password-reset wave after a security notice can triple a normal day's volume. On a free tier, the day is the binding limit, not the month, which is why a free plan you will grow out of should lead to paid plans with no daily cap.
Your own domain. A free tier that sends from a shared domain teaches mailbox providers nothing about yours. Mailgun's free plan allows 1 custom domain; AgentiSend's allows 3; SMTP2GO adds a limit of 25 emails an hour when the sender domain is unverified.
A footer you did not write. Loops puts its footer on free-plan emails, and Plunk puts one on marketing mail. A third-party footer on a password reset is a small thing until a customer asks why their bank-style message advertises a vendor.
Testing that does not count. Every test send you make to a real inbox uses quota and, if it bounces, counts against your domain. That is why the way a free tier handles tests matters as much as its size.
The free plans worth building on
1. AgentiSend
Best for: a new product that wants a free plan it can run in production, from its own domain, and a cheap first upgrade.
Free is 5,000 emails a month and 170 a day, 3 domains, 1 seat and 7 days of history, with no card and no end date. Real sends start once a domain verifies. Before that, two things work: any address at simulator.agentisend.com (delivered@, bounced@, complained@, suppressed@ and delayed@), which is charged nothing and never handed to a mail server, and [email protected], which mails your team members' sign-in addresses up to 20 times a day.
The simulator is the deliverability feature that matters on a free plan. A simulated bounce fires the same webhook as a real one, so you can prove your bounce handler works, yet simulated events never count toward your domain's bounce or complaint rates and the address is not added to your suppression list. You can run a hundred bounce tests on launch week without touching the reputation of a domain that has sent nothing real yet.
The free plan carries the same plumbing as the paid ones: a 2048-bit DKIM key generated when the domain is added, automatic suppression of hard bounces and complaints, a 7-day idempotency window, and published enforcement lines (warn at 2% bounces or 0.05% complaints, pause at 4% or 0.08%, over 7 days and never on fewer than 100 sends). When you outgrow it, Starter is $9 for 30,000 a month, and yearly billing takes 40% off any paid plan, which makes Starter $5.40 a month.
The full plan table is on the AgentiSend pricing page, and you can open an account at agentisend.com.
2. Brevo
Best for: small businesses that will stay on a free plan indefinitely and send under 300 a day, possibly with SMS later.
Watch out for: the first paid step is $9 for 5,000 emails, so paying buys less than the free plan sent. Idempotency keys last 30 minutes, and a repeat returns an error instead of the first result.
3. Mailjet
Best for: teams who want 6,000 free emails with a template editor and SMTP relay on the free plan.
Watch out for: Starter is $9 for 8,000, and inbound parsing needs Premium at 50,000 emails and above.
4. Mailtrap
Best for: developers who want to test in a separate sandbox and send real mail from the same vendor. The Email Sandbox free tier is 50 test emails a month, and the sending tier is 4,000. SOC 2 Type II is listed on every plan, including free.
Watch out for: 3 days of logs on the free sending plan.
5. Resend
Best for: projects that may adopt Resend's paid plans and want 30 days of retention on free.
Watch out for: 100 a day is the tightest daily cap among the larger free plans, and paid plans start at $20.
6. SMTP2GO
Best for: WordPress sites, routers and printers that can only send over SMTP.
Watch out for: past 1,000 a month further sends are rejected, and reporting covers 5 days.
7. Loops
Best for: SaaS teams who will use Loops for marketing anyway.
Watch out for: the free plan sends only to the 1,000 newest subscribed contacts, with a Loops footer.
Free in name only
| Service | Best for | Watch out for |
|---|---|---|
| Plunk | Projects that will pay per email later ($0.001 each) | Received mail counts toward the 1,000 |
| MailerSend | Teams that will buy SMS on Starter | Card required; 1 day of activity |
| Postmark | Trying the API before buying Basic at $15 | 100 a month covers testing, not users |
| Mailgun | Trying inbound routing (1 route on free) | 1 domain, 1 day of logs |
| SendGrid | Evaluating SendGrid for 60 days | It ends; free Email API retired 28 May 2025 |
| Amazon SES | AWS users with new-account credits | Sandbox to verified recipients until production access |
What 5,000 emails a month covers: a worked example
Take a SaaS app with 2,000 active users that adds 400 sign-ups a month. Here is what its transactional mail looks like under two login styles.
| Message | Password login | Magic-link login |
|---|---|---|
| Email verification (400 sign-ups) | 400 | 400 |
| Welcome email | 400 | 400 |
| Password resets (about 1 in 10 users) | 200 | 0 |
| Sign-in links (2,000 users, 2 logins a week) | 0 | 17,300 |
| Receipts (300 paying customers) | 300 | 300 |
| Monthly total | 1,300 | 18,400 |
The password-login app fits inside any free tier above 1,300, with room for a launch. The same app on magic links needs 18,400 a month, beyond every free plan here. On AgentiSend that is the $9 Starter plan (30,000); on Resend it is the $20 Pro plan. The login method, not the user count, decides which tier you need.
Check the daily figure too. If 400 sign-ups arrive on one launch day instead of spread across a month, verification plus welcome is 800 messages in a day, above every free daily cap on this list. If a launch is coming, upgrade the week before rather than the day after; AgentiSend's paid plans have no daily cap at all.
Using a free tier without hurting a new domain
- Verify the domain first and send from it. Publish SPF, DKIM and the return-path records, and add DMARC at
p=nonewith a report address. - Run every test against simulator or sandbox addresses. Bounces to real addresses you made up are real bounces.
- Grow volume over weeks. A new domain that jumps from nothing to its full free allowance on day one looks like a compromised one.
- Keep the suppression list. If you move providers later, export bounces and unsubscribes and import them, so you never re-mail an address that already failed.
Questions people ask
Which free email API has the highest monthly limit? Of the plans we read, Brevo at 9,000 a month (300 a day), then Mailjet at 6,000 and AgentiSend at 5,000.
Is a free tier bad for deliverability? Not in itself. What hurts is sending from a domain without SPF, DKIM and DMARC, or testing with fake addresses that bounce. Domain authentication works the same on a free plan as on a paid one.
Can I use a free plan in production? On AgentiSend, Brevo, Mailjet, Mailtrap and Resend, yes; none of them expires. SendGrid's free column ends after 60 days.
Do test sends count toward my bounce rate? On AgentiSend, sends to simulator.agentisend.com do not count toward domain rates or the plan. Sends to made-up real addresses count everywhere.
Sources
Pricing pages read 9 November 2026: resend.com/pricing, brevo.com/products/transactional-email, mailjet.com/pricing, docs.mailtrap.io (billing plans), loops.so/pricing, smtp2go.com/pricing, docs.useplunk.com/concepts/billing, mailersend.com/pricing, postmarkapp.com/pricing, mailgun.com/pricing, twilio.com/en-us/products/email-api/pricing, aws.amazon.com/ses/pricing. Documentation read 28 September to 10 November 2026: support.smtp2go.com (free plan), twilio.com/en-us/changelog/changes-coming-to-sendgrid-s-free-plans, developers.brevo.com (idempotency), dev.mailjet.com (Parse API), docs.aws.amazon.com/ses/latest/dg/request-production-access.html.