Add email-sending support

docs/configuring-playbook-email.md

@@ -0,0 +1,21 @@
+# Adjusting email-sending settings (optional)
+
+By default, this playbook sets up a [postfix](http://www.postfix.org/) 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 `matrix_mailer_sender_address` playbook variable).
+
+Furthmore, if you'd like to relay email through another SMTP server, feel free to redefine a few more playbook variables.
+Example:
+
+```yaml
+matrix_mailer_sender_address: "another.sender@example.com"
+matrix_mailer_relay_use: true
+matrix_mailer_relay_host_name: "mail.example.com"
+matrix_mailer_relay_host_port: 587
+matrix_mailer_relay_auth: true
+matrix_mailer_relay_auth_username: "another.sender@example.com"
+matrix_mailer_relay_auth_password: "some-password"
+```

docs/configuring-playbook.md

@@ -23,6 +23,8 @@ When you're done with all the configuration you'd like to do, continue with [Ins
 
 ## Other configuration options
 
+- [Adjusting email-sending settings](configuring-playbook-email.md) (optional)
+
 - [Storing Matrix media files on Amazon S3](configuring-playbook-s3.md) (optional)
 
 - [Using an external PostgreSQL server](configuring-playbook-external-postgres.md) (optional)