Posta

About Posta

Posta is a free, MIT-licensed email platform for developers and teams who want to send and receive application email on their own servers. It offers an SMTP server and an HTTP API for sending, plus inbound routes that pass incoming mail to an HTTP endpoint or forward it over SMTP.

Deliverability is handled in the same package. Posta generates SPF, DKIM and MX records for each domain, signs outgoing mail with DKIM and keeps checking DNS until it resolves. Hard bounces add an address to a suppression list so later sends are stopped, and per-server send limits and IP pools help protect sender reputation. Inbound mail can be checked with Rspamd or SpamAssassin, and attachments scanned with ClamAV.

Every delivery attempt is logged with the remote server's response and bounce reason. Held or failed messages can be released or retried from the dashboard or API, and signed webhooks are retried with backoff. Organisations can each run multiple mail servers. The site states there are no message caps, licence keys or phone-home behaviour, and setup uses Bun, PostgreSQL and a Clerk application for sign-in.