mail proxy to 3rd party using ssl

[rmombassa]

I am setting up nginx as POP3 mail proxy to two 3rd party mail servers.
Different domains, one of them uses SSL.

Since I do not have that 3rd party's SSL certificate I use my own company
certificate in nginx. That cert is properly signed but obviousy belongs to
another domain (our domain).

If I connect to the non-ssl server through nginx all works fine (port 110 on
nginx and 3rd party server).
 
If I connect to the ssl domain through nginx  (port 995 on nginx and 3rd
party server) I seem to not get a response from the 3rd party server. The
authentication routine on connection establishment is properly called by
nginx (correct uname/pw) and it returns that the user is OK (correct 3rd
party IP address is returned as well).

Using the email client without proxy works fine, meaning: uname/pw are
correct.

Questions:
- Is such configuration possible at all (ssl to 3rd party server without
having that server's certificate installed on nginx)?
- Is nginx in this configurtion a man-in-the middle? Could that be a
problem?
- Any idea how to further debug?

Thanks,
Rick

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,242473,242473#msg-242473