Problems using Mac Mail under Mountain Lion

Problems using Mac Mail under Mountain Lion

I'm having problems getting Mac Mail to work properly as my mail client.  Incoming mail is fine but the problem seems to be with the outgoing smtp mail server.  I have reset the port to 465 as instructed but to no avail.  I have a feeling it has something to do with OSX 10.8 Mountain Lion which I've heard is very problematic with smtp servers.  I had a similar problem with o2 as my server which was corrected by setting the port to 110 which I've also tried unsuccessfully.

Any clues?