matrix-docker-ansible-deploy/docs/configuring-playbook-email.md

Adjusting email-sending settings (optional)

By default, this playbook sets up an Exim email server through which all Matrix services send emails.

The email server would attempt to deliver emails directly to their final destination. This may or may not work, depending on your domain configuration (SPF settings, etc.)

By default, emails are sent from matrix@<your-domain-name> (as specified by the exim_relay_sender_address playbook variable).

Note: If you are using a Google Cloud instance, port 25 is always blocked, so you need to relay email through another SMTP server as described below.

Firewall settings

No matter whether you send email directly (the default) or you relay email through another host (see how below), you'll probably need to allow outgoing traffic for TCP ports 25/587 (depending on configuration).

Relaying email through another SMTP server

If you'd like to relay email through another SMTP server, add the following configuration to your inventory/host_vars/matrix.DOMAIN/vars.yml file (adapt to your needs):

exim_relay_sender_address: "another.sender@example.com"
exim_relay_relay_use: true
exim_relay_relay_host_name: "mail.example.com"
exim_relay_relay_host_port: 587
exim_relay_relay_auth: true
exim_relay_relay_auth_username: "another.sender@example.com"
exim_relay_relay_auth_password: "some-password"

Note: only the secure submission protocol (using STARTTLS, usually on port 587) is supported. SMTPS (encrypted SMTP, usually on port 465) is not supported.

Configuations for sending emails using Sendgrid

An easy and free SMTP service to set up is Sendgrid, the free tier allows for up to 100 emails per day to be sent. In the settings below you can provide any email for exim_relay_sender_address.

The only other thing you need to change is the exim_relay_relay_auth_password, which you can generate at https://app.sendgrid.com/settings/api_keys. The API key password looks something like SG.955oW1mLSfwds7i9Yd6IA5Q.q8GTaB8q9kGDzasegdG6u95fQ-6zkdwrPP8bOeuI.

Note that the exim_relay_relay_auth_username is literally the string apikey, it's always the same for Sendgrid.

exim_relay_sender_address: "arbitrary@email.com"
exim_relay_relay_use: true
exim_relay_relay_host_name: "smtp.sendgrid.net"
exim_relay_relay_host_port: 587
exim_relay_relay_auth: true
exim_relay_relay_auth_username: "apikey"
exim_relay_relay_auth_password: "<your api key password>"

Troubleshooting

If you're having trouble with email not being delivered, it may be useful to inspect the mailer logs: journalctl -f -u matrix-exim-relay.