All Mastodon servers hosted in Masto.host comes with a @masto.host email address to send your server notification emails. This email address is unique to your server, but it does not receive emails.
If you want to use a different email address, you will need to email info@masto.host to request that change and provide the following SMTP details:
- SMTP Host
- SMTP Port
- Login
- Password
- From Address
Notice that a Mastodon server can send many emails, so you should use a high volume sending SMTP because most SMTP services limit the number of emails you can send per hour/day. A service like MailGun, Amazon SES, SendGrid, MailerSend and others would be a good solution.