geekster:
> After comparing successful emails to non-successful emails. It seems like
> what is happening is that the 2 servers in question couldnt get the TLS
> session established and then the sender disconnects. but the question is
> why?
Did you make changes to TLS ciphers and protocols settings?
$ postconf -n | egrep 'tls.+(cipher|protocol)'
BTW Postfix does not implement TLS, that's done in the OpenSSL
library. If you run Postfix with a very old OpenSSL version then
you may suffer from compatibility issues.
Wietse
