No problem. I learnt the hard way and DID spend a while thinking there was something seriously wrong with my new mac. My brother sorted me out, thankfully.
Opeing Little Snitch worked for me too. I had a feeling it had something to do with it.So. Go to yr Applications folder and open Little Snitch. Scroll down and you'll find that some Mail ports are checked "deny". Uncheck them. Thats it!