- Fast SMTP processing & storing - approximately 70-100 emails per second depending on CPU, network speed & email size, easily handling tens of thousands of emails
- SMTP relaying / message release - relay messages via a different SMTP server including an optional allowlist of accepted recipients ([see wiki](https://github.com/axllent/mailpit/wiki/SMTP-relay))
- Optional SMTP with STARTTLS & SMTP authentication, including an "accept anything" mode ([see wiki](https://github.com/axllent/mailpit/wiki/SMTP-with-STARTTLS-and-authentication))
Static binaries can always be found on the [releases](https://github.com/axllent/mailpit/releases/latest). The `mailpit` binary can extracted and copied to your `$PATH`, or simply run as `./mailpit`.
Mailpit's SMTP server (by default on port 1025), so you will likely need to configure your sending application to deliver mail via that port. A common MTA (Mail Transfer Agent) that delivers system emails to a SMTP server is `sendmail`, used by many applications including PHP. Mailpit can also act as substitute for sendmail. For instructions of how to set this up, please refer to the [sendmail documentation](https://github.com/axllent/mailpit/wiki/Configuring-sendmail).
I had been using MailHog for a few years to intercept and test emails generated from several projects. MailHog has a number of performance issues, many of the frontend and Go modules are horribly out of date, and it is not actively developed.
Initially I tried to upgrade a fork of MailHog (both the UI as well as the HTTP server & API), but soon discovered that it is (with all due respect to its authors) poorly designed. It is in my opinion over-engineered (split over 9 separate projects), and performs very poorly when dealing with large amounts of emails or processing emails with an attachments (a single email with a 3MB attachment can take over a minute to ingest). Finally, the API transmits a lot of duplicate and unnecessary data on every browser request, and there is no HTTP compression.
