message received on freshly configured account is not notified

If you configure a new account on thunderbird, any new mail is not notified (even if you press "get messages") until thunderbird is restarted.

traffic capture shows only some IDLE commands, but no FETCH is issued. should check if the Listener is properly added and acted upon.

(from redmine: created on 2015-06-24, closed on 2015-07-08, relates #7161 (closed))