SMTP refusing to accept password

Cannot get smtp to accept password in Thunderbird. Have used it for years on two different computers. Works fine on my account. Will not work on wife's account on her machne. All settings the same ( except accountname of course). She can receive emails fine, but any attempt to send throws box for password.

I have changed password 3 times now. Emails send and receive fine through mail on xfinity website, so I know the password is correct.

Suggestions?