We are having issues with Office365 users sending to our exchange server. We are a small exchange shop. No office365 here. But we have had 3 DIFFERENT domains sending emails our direction receiving the '550 4.4.7 QUEUE.Expired; message expired' returned email error messages. When using gmail or any other mail service we've tried this issue does not happen. What does Office365/hosted exchange look for differently than any other service?
Regards,
Jay