14 Nov 2022

Self-hosted Mastodon SMTP configuration

Since masto.host has signups disabled at the moment, I tried deploying Mastodon to Fly.io using tmm1’s flyapp-mastodon instructions. It worked surprisingly well, by which I mean about half of the documented commands were using removed option flags, I had to debug sidekiq restarting in a different random region constantly, and email sending didn’t work at all.

I eventually got email sending working via Postmark, but the Mastodon documentation is extremely unhelpful about how to configure sending emails: it just lists all possible ENV vars and then moves on.

Here’s the env var configuration that worked for sending emails from Mastodon through Postmark, for me:

SMTP_LOGIN="<Postmark SMTP Token Access Key>"
SMTP_PASSWORD="<Postmark SMTP Token Secret Key>"
SMTP_FROM_ADDRESS="<Postmark Sender Signature verified email address>"

Hopefully that helps someone (or at very least future me) set up outgoing emails on a self-hosted Mastodon server in the future.