Resend
Checked on 17 Oct 2026Free tier: Free $0/mo: 3,000 emails/month, 100 emails/day, 3 domains, 3 inboxes.
- Auth: API key (Bearer)
- Serving public users: Yes.
- Source: resend.com
Free email APIs (2026)
Transactional email APIs with a free sending quota. 4 providers, each with the free-tier text from its official pricing page and the date we checked it.
4 free email APIs compared
Brevo (transactional email)
Checked on 17 Oct 2026Free tier: Free plan forever, no card; once account is approved, send up to 300 emails per day.
- Auth: API key (api-key header) / SMTP
- Serving public users: Yes.
- Source: www.brevo.com
Mailgun
Checked on 17 Oct 2026Free tier: Free $0/mo: 100 emails/day included.
- Auth: API key (Basic auth)
- Serving public users: Yes.
- Source: www.mailgun.com
Postmark
Checked on 17 Oct 2026Free tier: Free developer tier: 100 emails/month, no overages, no credit card.
- Auth: Server token (X-Postmark-Server-Token)
- Serving public users: Yes (low volume).
- Note: Testing/low-volume only.
- Source: postmarkapp.com
Each free tier was read from the provider’s official pricing or limits page on 17 Oct 2026 and is linked as the source. Anything the page does not state is written as unknown. Free tiers change often, so confirm before you build on one.