Incorrect settings in Mail

I believe that I have messed up settings in my Mail accounts on my iMac by ignorantly changing something. The problem is in outgoing messages where I will get the screen below. Don't know what it means. email sending must match one "auth." Does that mean "authorized"? When and where did I authorize? The meaning of the field names in settings are not always clear to me and they do not match the fields in settings on my iPad where there is no problem.

[Edited by Moderator]