How and where do I do thisYou need to check your e-mail settings for incoming (POP3) and outgoing (SMTP) servers

These settings will be found in the configuration of your specific mail client software. For example, in Microsoft Outlook 2007 they are accessed via:

Select Tools menu.
Select Account Settings... menu item.
Select account of interest.
Click Change... button.

If you are using another mail client, consult its built-in help.