This article will show how to add SMTP suport to an existing mail account setup in Mail (for Apple Mac OSX 10.5 (Leopard))
Beginning
From the menu bar select Mail and then Preferences (or Applekey and ,)
Click The Accounts button at the top of the new screen.
From the left hand side select the account you wish to add SMTP support to
Select 'Edit Server List from the 'Outgoing Mail Server (SMTP)' drop-down list
Click the + icon, to add a new SMTP server.
Fill in your SMTP address, for example smtp.YOURDOMAIN (please replace YOURDOMAIN with your actual domain name).
Click the Advanced tab.
Select Password as the authentication type
Fill in your SMTP username and password
Click OK to save the new details.
Ensure you select the newly added SMTP server as the SMTP server to use.
Advanced
It has come to our attention that some ISPs are starting to block the standard SMTP port.
With this in mind if you get this problem please try sending using port 2525, as shown below