How do I change SMTP password?

Go to the Accounts section of the preferences in Mail, then select an account and in the Account Information tab click the Outgoing Mail Server (SMTP) menu and choose "Edit SMTP Server List." In here you should be able to select an SMTP server and set the password, port, username, and other details in the tabs below the list.

Account Information does not show an "Outgoing Mail Server" choice.