Help! Can't send mail!!!

Hey guys!

I have not been able to send email from my MAC address for the past two days. It takes forever to send, and then I get an error message saying that the server can't send the message. My computer is 3 weeks old, any ideas? Oh, I have the 24 inch, 3 gig IMac. THANKS IN ADVANCE for your help!!!!

1) Go to mail->preferences->accounts
2) in the Account information you will see Outgoing Mail Server (SMTP)
3) There is a drop down box on smtp.mac.com, select edit server list
4) click on Advanced
5) You will see the port, change it to 587
6) Close out of Mail completely
7) Open Mail back up again
8) Send yourself a test email.

Hope this helps!