Can Nginx route SMTP based on login credentials?

[spockdude]

spockdude Wrote:
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> I have several users using the same mail host (smtp.example.com) to
> send outbound email using authentication.  I would like to split it up
> into several outbound servers and assign specific users to specific
> mail servers without having to change the mail host information in
> each user's email client.  Can Nginx do this or does it always just
> spread that traffic between all backend servers?


It seems this list is not very active, but I'll go ahead and answer my own
question.  It *does* appear that the above functionality is supported
according to this page:

https://www.nginx.com/resources/admin-guide/mail-proxy/

It says "If authentication is successful, the authentication server will
choose an upstream server and redirect the request."

If I'm understanding this correctly, I just need to create an authentication
server that instructs Nginx which upstream server to send the request to
based on the user's credentials.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,272088,272141#msg-272141