disconnect method
Disconnects from the mail service.
Also compare connect.
Implementation
Future<void> disconnect() async {
final futures = <Future>[
stopPollingIfNeeded(),
_incomingLock.synchronized(
() => _incomingMailClient.disconnect(),
),
_outgoingLock.synchronized(
() => _outgoingMailClient.disconnect(),
),
];
_isConnected = false;
await Future.wait(futures);
}