Custom 'Mail From' Domains

[Dave Swift]

When using the built-in SMTP server, it would be wonderful to be able to add a custom mail-from domain.

Use case: often people use Google Workspace (or similar) for their person-to-person work mail, but need a mail server for bulk email.

Bulk emails need to include a return-path header, which should match the mail-from header.

When using a service like Mailgun or Amazon SES, you can specify a custom mail from domain, typically a subdomain like send.domain.com

You can still set your from header to your primary domain, in this case, domain.com. But your Mail from and return-path headers can match.

To be more specific, with Mautic as an example. Mautic can monitor bounces using an IMAP inbox, but the From address must be able to send from that monitored inbox's domain or an error occurs when trying to send, the errors would look something like this:

Failed to send to test-user@example.com: Expected response code 250 but got code "550", with message "550 Authenticated user johndoe@domain.com cannot send mail as bounce+bounce_id@bounce.domain.com"

So you can't simply setup a From address of johndoe@domain.com and monitor for bounces on bounces@send.domain.com (which would be the standard practice at all major ESPs).

The only option to work around this currently is to pay for an additional account at Google Workspace to manage bounces, but even this solution is short lived as Google is ending support for traditional authentication for IMAP accounts later this year.