Hi, This is just a wild guess...
> I'm also pretty sure it's not a network issue. After passing > billions of packets there isn't a single error. I'm also pretty sure > DNS is configured properly. Have you checked the connection between postfix and the exchange machines? After some years, a cable can get bad, lousy, and the packets would not pass so reliably anymore. After moving a machine/wandering around a rack cabinet, one may have step on a cable and disconnect it or damage it. Bests, Olivier
