reverse proxy SMTP - How distinguish MUA and MTA

Rainer Duffner rainer at
Thu Jun 4 19:40:46 UTC 2015

> Am 04.06.2015 um 20:13 schrieb dethegeek <nginx-forum at>:
> Hi
> Still building a nginx reverse proxy for my mail servers. Thanks to the
> community, I now have a secure connection between nginx and my backend mail
> server. 
> POP and IMAP are working well, from a MUA to my server.
> I'm wondering how nginx can manage SMTP coonnections as it is used by both
> MUA and MTA.
> A MUA must authenticate before sending mails; and my http_auth backend is
> able to authenticate users.  More precisely, the authentication backend
> answers a server (auth-server / auth-port) depending on the domain of the
> destination email address.
> Now I guess I have to accept incoming emails without authentication if the
> client is a MTA, but I don't find a obvious way to distingish a MUA and a
> MTA and let mu auth backend behave depending on that.
> How to achieve that ?

MUA = Port 587 + 465
MTA = Port 25

Maybe use something like Haraka for SMTP?
It’s supposed to be for SMTP-servers what NGINX is for Webservers ;-)


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