The best free SMTP server depends on how much you send per day. Among the free plans checked for this post, Brevo allows the most per day (300 emails, so up to about 9,000 a month if you send every day), and Mailjet has the largest stated monthly allowance (6,000 emails a month, capped at 200 a day). Resend (3,000 a month, 100 a day) and Elastic Email (3,000 a month) follow. A Gmail mailbox works as a free SMTP server for a few personal messages, but it is not meant for app mail. Every service below expects you to authenticate with SMTP credentials, and most expect you to add a sending domain and publish DNS records first.
Free SMTP Relay Limits Compared (as of October 2026)
Each row below comes from the provider’s own pricing or documentation page, fetched in October 2026. Free plans change often, so confirm on the linked page before you build on a number. Two former staples, SendGrid and Amazon SES, changed their free offers; the notes after the table explain what is left.
| Provider | Free allowance | Type of plan | SMTP relay | Branding on free plan | Catch |
|---|---|---|---|---|---|
| Mailjet | 6,000 emails/month, 200/day | Permanent free plan | Yes (in-v3.mailjet.com) | Mailjet logo (the no-logo feature starts on Essential) | Daily cap, 1,000 contacts |
| Resend | 3,000 emails/month, 100/day | Permanent free plan | Yes (smtp.resend.com) | Not stated on the pricing page | 3 domains, 30-day data retention |
| Elastic Email | Up to 3,000 emails/month | Free plan, no card needed | Listed in plan features | Not stated | 3-day log storage, up to 1,000 contacts |
| Brevo | 300 emails/day | Permanent free plan | Yes (ports 587, 2525, 465) | Not stated | Daily cap, sending starts after account approval |
| SMTP2GO | 1,000 emails/month, 200/day | Permanent free plan | Yes | Not stated | 25 emails/hour until you verify a sender domain |
| Mailgun | 100 emails/day | Permanent free plan | Yes (smtp.mailgun.org) | Not stated | 1 custom domain, 1-day log retention |
| MailerSend | 500 emails/month | Permanent free plan | Yes | Not stated | 1 domain, 1-day activity retention |
| Postmark | 100 emails/month | Developer plan that “doesn’t expire” | Yes (smtp.postmarkapp.com) | Not stated | Tiny volume, meant for testing |
| Zoho ZeptoMail | “First credit is free” (10,000 emails) | One-time credit | Yes (smtp.zeptomail.com) | Not stated | Credits are valid for 6 months |
| Twilio SendGrid | 100 emails/day for 60 days | Trial only | Yes | Not stated | Free plan retired in 2025 |
| Amazon SES | Up to $200 in AWS Free Tier credits | Credits for new AWS accounts | Yes | None | Sandbox limits until you request production access |
| Gmail | 500 emails/day | Mailbox | Yes | None | Not for app mail |
“Not stated” means the provider’s pricing page does not mention it, not that the provider has none.
What Changed for SendGrid and Amazon SES
SendGrid no longer has a free plan. Twilio’s changelog says it is “retiring its Free Email API and Free Marketing Campaigns plan starting May 27, 2025.” What exists today is a trial: SendGrid’s Email API page says “Start free with 100 emails a day for 60 days then upgrade to a paid plan.” If a blog post still lists SendGrid as a permanent free SMTP server, its numbers are stale. For the paid side, see SendGrid pricing.
Amazon SES no longer has a recurring free allowance for new accounts. Older guides cite 3,000 free message charges a month. SES’s pricing page now says new AWS customers receive “up to $200 in AWS Free Tier credits,” that “the free plan will be available for 6 months after account creation,” and that new SES accounts “will start on the Essentials plan beginning July 21, 2026.” A new SES account also starts in a sandbox. Per the SES documentation, you can then send only to verified addresses, a maximum of 200 messages per 24-hour period and 1 message per second, until AWS approves a production-access request.
Notes on Each Free SMTP Provider
Mailjet. The highest monthly allowance in the table, and the pricing page lists “APIs, SMTP Relay, Webhooks” on the free plan. The catches are the 200-a-day ceiling and the Mailjet logo, which only disappears on the Essential plan and above. Mailjet’s SMTP documentation lists ports 25, 80, 465, 587/588 and 2525, with your API key and secret key as the credentials.
Resend. A good fit for a developer who wants an API and SMTP in the same account. Resend’s SMTP documentation uses resend as the username and your API key as the password, on ports 25, 465, 587, 2465 or 2587. The 100-a-day cap is the practical limit: a launch-day email blast will stall. More detail in Resend pricing.
Elastic Email. The pricing page advertises a plan “for up to 3,000 emails/month” with no credit card required, with shorter log storage than paid plans (3 days versus 7 days on Pro). Its SMTP relay appears in the plan feature list on that page, so check the exact plan you land on when you sign up.
Brevo. A daily cap of 300 emails suits steady low-volume sending better than a monthly bucket, because a quiet week does not give you extra room later. Brevo’s SMTP integration docs say to “use an SMTP key, not an API key, for SMTP relay connections,” and list ports 587, 2525 and 465. The 300-a-day figure is from Brevo’s email API page. See Brevo pricing for plan detail.
SMTP2GO. Its limits page states 1,000 emails a month, 200 a day, and “25 emails per hour (this hourly cap is removed automatically once you verify your sender domain)” in the SMTP2GO sending limits article. That hourly cap is a trap for first tests: verify the domain before judging the service.
Mailgun. The pricing page gives 100 emails a day, 1 custom sending domain and 1 day of log retention. It is enough for a staging environment or a hobby form, and thin for anything you need to debug after the fact. The Mailgun SMTP documentation lists smtp.mailgun.org with ports 25, 465, 587 and 2525, and recommends 587. See Mailgun pricing for the paid tiers.
MailerSend. The free plan gives 500 emails a month, 1 domain and 1-day activity retention, with the pricing page listing “Email API and SMTP relay.” It is a modest allowance, in line with the other small plans here.
Postmark. The free developer plan is 100 emails a month and, in Postmark’s words, “doesn’t expire.” That is a test environment, not a production quota. Its SMTP guide gives smtp.postmarkapp.com on ports 25, 2525 or 587. More in Postmark pricing.
Zoho ZeptoMail. This is a credit, not a plan: the first 10,000-email credit is free, and email credits are valid for 6 months. After that you pay per credit. ZeptoMail’s SMTP setup page gives smtp.zeptomail.com on port 465 (SSL) or 587 (TLS).
Catches Every Free SMTP Tier Shares
A free SMTP server is cheap to start and awkward to rely on. These are the problems developers run into most often:
- Daily caps hit mid-day. A 100-a-day limit means a burst of password resets can use up the allowance by lunchtime, and later users get nothing until the window resets.
- Shared IP reputation. Free accounts send from pools shared with other free accounts. Another tenant’s spam can cost you inbox placement. Read how a shared IP compares with a dedicated one.
- New-account review. Amazon states plainly that it must “consider each request carefully” before granting production access, and SMTP2GO throttles unverified senders. Expect friction on day one.
- Authentication is on you. Providers ask for a sending domain and DNS records; mail from an unauthenticated domain lands in spam. SPF and DKIM are the starting point.
- Branding and short logs. Mailjet adds its logo on the free plan, and several plans keep logs for one day, which makes debugging a bounce a day later impossible.
- Limited support. Several free plans route support through tickets only.
Free SMTP services expect a verified sending domain. Amazon SES requires you to “verify all identities that you use as ‘From’” addresses, and SMTP2GO caps unverified senders at 25 emails an hour. Budget time for DNS records before your first real send.
For paid options once you outgrow these limits, see paid transactional email services, or what Reddit recommends for community opinions.
Gmail and Microsoft 365 SMTP Servers: Free, but Not for App Mail
A mailbox gives you an SMTP server you already own. The tradeoff is that it is built for people sending messages, not software.
- Gmail. Google’s help page says you cannot send “more than 500 emails in a single day” from a personal account. Google Workspace allows 2,000 messages a day per user, with external recipients capped at 3,000 a day. Setup details are in Gmail SMTP settings, and the limits are explained in Gmail sending limits.
- Microsoft 365. Client SMTP submission uses
smtp.office365.comon port 587 with TLS, and is limited to “10,000 recipients per day. 30 messages per minute.” Microsoft also notes that basic authentication for client submission is “scheduled for deprecation” and that SMTP AUTH is disabled for organizations created after January 2020 unless you enable it per mailbox. See Office 365 SMTP settings. Consumer Outlook.com accounts have different limits and are not covered here.
Mailbox SMTP is not for app mail. Mailbox providers cap daily volume, tie sending to one person’s account, and may suspend that account when you hit limits. Google says users who exceed limits face suspension “for up to 24 hours.”
Use a mailbox for a handful of messages you would send by hand. Use a dedicated sending service for anything triggered by your app.
Free SMTP Server Software: Mailpit and Self-Hosting
The phrase “free SMTP server” also covers software you run yourself. Two very different things live here.
Local test servers. Mailpit describes itself as “a small, fast, low memory, zero-dependency, multi-platform email testing tool & API for developers.” It does not deliver mail to real recipients. Per the install docs, “Mailpit listens by default on port 8025 for the web UI, and port 1025 for SMTP.” Point your app at localhost:1025 in development, and you can inspect every message in the browser without risking a send to a customer. That is the right free SMTP server for development and CI.
Self-hosting with Postfix. Postfix is free, open-source mail server software, and it works. Three problems keep it from being a free replacement for a sending service:
- Port 25 is often blocked. Google Cloud states that “connections to destination TCP Port 25 are blocked when the destination is external to your VPC network.” Azure blocks outbound port 25 on VMs for most subscription types, and Amazon EC2 “throttles email traffic over port 25 by default.” Read more in SMTP relay.
- You need reverse DNS. Receiving servers check that your IP resolves back to your hostname; see reverse DNS.
- A new IP has no reputation. Plan to warm up a new IP over weeks before volume works.
The cloud vendors point the same way: Microsoft recommends “authenticated SMTP relay services” on port 587, and Google notes that third-party providers help “your IP reputation score.”
How to Choose a Free SMTP Server by Scenario
| Scenario | Good starting point | Why |
|---|---|---|
| Password resets for a side project | Resend or Mailjet | API and SMTP, a daily cap that covers low traffic |
| WordPress contact form | Brevo or SMTP2GO | Daily caps of 300 and 200 fit a form that gets a few submissions a day |
| Staging or local development | Mailpit | Catches everything, delivers nothing |
| Newsletter to a few hundred people | Mailjet | 6,000 a month, 200 a day, but expect its logo |
| App prototype on AWS | Amazon SES | Credits for new accounts, but plan for sandbox approval |
| Cold outreach | None of the above by default | Read each provider’s acceptable use policy first |
On cold outreach: SES’s production-access form asks you to agree “to only send email to individuals who’ve explicitly requested it,” and other providers set their own rules, so read the terms before you send unsolicited mail through any free plan.
Connecting to a Free SMTP Relay
Every relay uses the same five settings, whatever the brand:
Host: smtp.example.com
Port: 587 (STARTTLS) or 465 (implicit TLS)
Username: as shown in your provider's dashboard
Password: your SMTP key or API key
From: [email protected] (an address on your verified domain)The username and password are how the relay checks that you may send through it; SMTP authentication explains that exchange. Choose port 587 or 465 rather than 25, which many networks block. Some providers use the API key as the password (Resend, for example), others issue a separate SMTP key (Brevo’s documentation says to use an SMTP key, not an API key). After saving the settings, test the connection before pointing real traffic at it.
Frequently Asked Questions
Is there a completely free SMTP server?
Not one you can rely on at any volume. Several services keep a permanent free plan, such as Mailjet, Resend, SMTP2GO, Brevo and Mailgun, but all of them cap volume. Software you run yourself, such as Postfix or Mailpit, costs nothing to install, but Postfix needs an unblocked port 25 and a clean IP, and Mailpit never delivers real mail.
Which free SMTP server has the highest limit?
Among the plans checked in October 2026, Brevo allows the most per day at 300 emails, about 9,000 over a 30-day month if you use it every day. Mailjet has the highest stated monthly figure at 6,000 emails a month (200 a day). Resend and Elastic Email follow at 3,000 a month.
Can I use Gmail as a free SMTP server?
Yes, for personal volume. Google’s help page says you cannot send “more than 500 emails in a single day” from a personal account. It works for a few messages, but it is the wrong tool for password resets or receipts. See Gmail SMTP settings for the configuration.
Is a free SMTP relay safe for production?
Only for low-stakes mail. Free plans share IP pools, cap volume, keep logs for a day or a few days, and offer little support. For anything customers depend on, such as sign-in codes or receipts, use a paid plan with longer logs and a clear support path.
Do free SMTP services add branding to my emails?
Some do. Mailjet’s pricing page says the “No Mailjet logo” feature starts on the Essential plan, so free plans carry its logo. For the other providers in the table, the pricing pages do not state branding either way, so check the plan terms before sending to customers.
Can I run my own SMTP server for free?
You can install Postfix at no cost, but delivering mail is the hard part. Major cloud platforms block or throttle outbound port 25, a new IP has no sending reputation, and you need correct reverse DNS and authentication records. For development, Mailpit is the easy free option, because it only catches mail.
I’ve spent my career building software at scale with a soft spot for email: deliverability, lifecycle campaigns, and getting messages to actually land. I started Coldletter to fix what bugged me about transactional and marketing email tools. I’m based in Vancouver.