It 'looks like' he has the right server defined, but it has no authentication. usually SSL/TLS or STARTTLS and normal password.. If you use same server, see if his is similar to yours.

As a comment, that screenshot on the right indicates that his SMTP server should be mail.twc.com. But I don't know which it should be. Again, if you use same email provider, compare to yours.

BUT, to be safe, change the DESCRIPTION field content to ensure the two have different names.

David, you rock! Your first two emails helped me solve the issue, which is great, because I couldn't find a DESCRIPTION field on either of the account settings pages. Thanks again for hanging in with me, and by the way, the SOLVED THE PROBLEM button doesn't work, so I have to use this way of saying it's solved. Thank you so much! Linda

Aw, shucks, ma'am... I was glad to help :) (as an aside, the description field is in the SMTP server setup pane. Both of the had the same description. It's only documentation, but the most common reason for the message your husband received is when a user has one email address on the incoming server settiings and a different on on the SMTP settings. This commonly happens when a person has two or more accounts and gets them crossed. By putting the email account in description field, the likelihood is minimized because the error will be obvious when viewing link to SMTP settings from the account pane. As it is, that wasn't his problem.)