Outlook 2010

Open Outlook. Click the File tab on the ribbon and then click Info on the left.

Select your email account from the list, then click Account Settings and choose Account Settings in the menu that appears.

Select your email account and click the Change button.

Click the More Settings button, then click the Outgoing Server Tab

Check the box that says "My Outgoing Server (SMTP) Requires Authentication. Make sure the box below it that says "Use Same Settings As My Incoming Mail Server" is also checked.

Click The Advanced Tab and change the Outgoing Server Port number from 25 to 587.

Click OK, click Next then click Finish.

You're done!