When you've complete this task, go back into the Tools Dropdown, Accounts, Properties Button, Server Tab,
then look at the bottom for a checkbox that says "My Server Requires Authentication" (that needs to be checked).

***If you're able to receive emails but not send due to an error that continues to pop up and
the email stays in the outbox, please call your ISP (internet Service Provider: AT&T, SBC Global, etc.)
and ask them to lift the restrictions on port 25.

If the problem STILL persists and you still cannot connect, you will need to verify that you don't have a Firewall that is blocking the email program from sending and receiving on that computer. (Or that you don't have a network level firewall that is blocking any ports (like 25 and 110 which POP3 Email Accounts use)

In some cases your email program may be blocking your outbound emails.

These problems will require some technical help from an IT person or someone you trust to handle your computers, such as a friend or family member that is experienced in working with computers.