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