Users didn't get mails sent to DG

brilwjm

Hi, Guys:
I encourter a problem of Exchange categorizer, I found many time from Internet,but there is no solution, now I post it up, Please help to to see this problem.
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There are some users in the Distrbution Group claim that he/she didn’t receive the mails.
We have confirmed the following issues:
1. User is the member of the Distribution Group.
2. No users have duplicated X.400 addresses with this user.
3. Sender got no NDRs.
4. From the Message Tracking log searched by MSG-ID of Exchange Server on which Sender resides, the user is not in the recipients list which Exchange server expands.
So, for the Distribution Group. We have set one Exchange Server as it's expansion server, thus enabling Diagnostic Log: MSExchangeTransport\ Categorizer on it.