The following is a simple tutorial on how to setup SMTP AUTH in Outlook. The screenshots taken are from Outlook 2002 but are applicable to most versions of Outlook.
Home
Beginning
First of all you need to open the mail program and then select the "Tools" option. From this menu select the "E-mail Accounts" option. This allows you to setup and configure your mail accounts.
Selecting your mail account providers
Select "View or change existing email accounts", click Next.
You will then be able to choose which email address you wish to edit, and click Next.
Configuring servers
You need to make sure you have the SMTP server filled in as detailed below. You should already have the POP3 server name set. For the SMTP server enter:
smtp.yourdomainname
Please refer to the SMTP welcome mail you will have received when SMTP was setup for you.
Entering the authentication settings
Click the "More settings" button. Select the "Outgoing server" tab, and click the "My outgoing server (SMTP) requires authentication" checkbox. Select "logon using" and enter your SMTP username and password.
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 instead of 25 in the following part of the setup