Are you by chance running antispam or antivirus software that might be intercepting the message for some reason and deleting or quarantining it? If so, check the log/archive files for that software and see if the messages are present.
One other option would be to turn on diagnostic logging and then check the event logs for message and transport-related events.
Dig Deeper on Exchange Server setup and troubleshooting
Related Q&A from SearchExchange Staff
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.