contact widget with smtp - is it possible?

Sometime during the summer our contact plugin stopped working - no doubt a result of some update or a change at our host. We used Contact 7 and WP-SMTP-Mail. Although the contact form stopped working, all of our system mail continues to work fine. We also use "subscribe by email" and that works fine too.

Today, I returned to the contact problem. I downloaded th WPMU Contact Widget and activated it on a subsite. It didn't work . "Mail not sent".

I see forums all over the place discussing this issue, but with no clear, conclusive, easy-to-effect solution. Do we have to abandon SMTP to get a contact form to work?