I have mailboxes configured via imap and occasional the DSL connectivity fails for a short time. mailwatch displayes then a red - not entry symbol (like the one at the outlet of a one-way road) .
But when the DSL comes back and email checking is back to normal it doesn't remove this red sign. Only a new login or reboot resets this.

The indication about a disturbance with the mail checking should be reset automatically when the mail checking works again.