The certificate says I'm trying to connect to the internal server name but my certificate is for "mail.externaldomain.com". I have split DNS running so I can reference the external name internally.
Without knowing what your public domain name is I cannot test to see if public DNS is setup properly. What is it?
I'm not trying to reference the server from public DNS. I'm trying to reference it from internal DNS.
So you're saying it's a DNS issue though?