I just noticed that we are not receiving emails today. nothing changed, everything has been working fine until a couple hours ago.

i tried checking the admin, and I'm getting an error when i go to mail queues:

Message: system failure: exception during auth {RemoteManager: mailhost.toqen.com->zimbra@mailhost.toqen.com:22}
Error code: service.FAILURE
Method: ZmCsfeCommand.prototype.invoke