I believe the cert that is being used for SMTP is /opt/zimbra/conf/smtpd.crt. You will have to export the cert using openssl in order to install it anywhere else I think.
I don't know if that will help because it seems like the client isn't even trying to initiate the TLS session because you do not get a prompt. Just for the sake of taking a MS product out of the loop have you tried using Thunderbird or some other mail client? |