SMTP Mail Settings – for MAC OSX

the correct settings are:

In Mail versions older than 3 - go to mail | preferences | accounts
down the bottom select Server Settings button
then change it as per above image

In Mail version 3 +
Choose Preferences from the Mail menu.
Click Accounts in the Preferences window.
Select (highlight) your account on the left side of the window if you have more than one account.
Click the Account Information pane.
>From the "Outgoing Mail Server (SMTP)" pop-up menu, choose Edit Server List. A new sheet appears similar to this:

Select the SMTP server that matches your email provider. (Note: If you don't see a matching server choice, click the "+" button and add a new one using the  settings from your email provider.)
Click the "Advanced" pane (to the right of "Account Information").
Verify that the port, authentication, user name, and password settings also match what your e-mail provider has supplied
you. If not, replace them with the correct information. (The password will always appear as a series of bullet characters.)

ie - smtp.australisit.net
port 25
NO SSL (macs turn it on by default)
Authentication = none
Username = blank
pass = blank