Ignore deleted mails in IMAP unread count (#6394) (#6395)

Message deletion in IMAP is a two step process: first delete, then expunge.
Deleting a message just sets a flag that usually makes the mail client hide
the message. It is the expunge that actually removes the message.

Thus, exclude the deleted messages so that the unread count matches up with
that of most mail clients.

homeassistant/components/sensor/imap.py

@@ -85,7 +85,7 @@ class ImapSensor(Entity):
         try:
             self.connection.select()
             self._unread_count = len(self.connection.search(
-                None, 'UnSeen')[1][0].split())
+                None, 'UnSeen UnDeleted')[1][0].split())
         except imaplib.IMAP4.error:
             _LOGGER.info("Connection to %s lost, attempting to reconnect",
                          self._server)