PostalSend application email through SMTP or an HTTP API on your own infrastructure.
100% free open-source software (GPLv3). Unlimited emails, domains, and mail servers.
Developer tools
Brevo
Free optionBrowser
Send signup confirmations, password resets and other transactional emails through an API or SMTP.
What you can use it for
Send signup confirmations, password resets and other transactional emails through an API or SMTP.
- Send transactional emails through a hosted API or SMTP.
- Lasting free plan for one account owner.
Workflow coverage and comparison notes
Low-volume outbound transactional email via API or SMTP. Brevo provides 300 free sends/day, shared with campaigns, for one user with branding. Not a complete Resend integration replacement: receiving, SDK compatibility and webhook behaviour need migration checks. Both services offer free plans.
Before you switch
Proprietary hosted service; not open source. The 300-send daily allowance is shared with campaign emails, resets daily and does not roll over. Free emails carry Brevo branding. Excess transactional sends may be queued; emails beyond the retry queue can be undelivered. Account setup and sender authentication are required. Higher volumes and extra users cost money. This covers outbound transactional sending, not proven parity with Resend inbound processing, SDKs or webhook behaviour. Resend also has a free plan; switching is optional. Not hands-on tested by us.
Alternatives to these paid apps
Each comparison covers the workflow described above, rather than every paid feature.
More for the same workflow
See alternatives →Postal
opensend.ccSend transactional emails through an API on infrastructure you control.
Free open-source (Apache-2.0). Unlimited emails (backed by AWS SES at $0.10/1k).