If you are seeing something similar in your SMTP logs then there could either be a,
1. Network problem in your network
2. Network problem in the sender's network
3. A firewall problem in your network
Getting the error message as "rejected timeout waiting for input from wa4ehsobe004.messaging.microsoft.com" in the mail logs.
1. Capture the packets while there is email traffic from the affected source. The packets should be captured at both end points and the firewalls ( if any ) to get a complete picture. This should tell you where the problem lies.