Can Nginx route SMTP based on login credentials?

spockdude nginx-forum at
Wed Jan 25 16:13:16 UTC 2017

spockdude Wrote:
> I have several users using the same mail host ( 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:

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:,272088,272141#msg-272141

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