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Distribution Group member not receiving emails sent to group address (Exchange 2016)

Gabriware 101 Reputation points
2020-08-04T11:20:02.327+00:00

Hello all, I’m having a really weird problem with a distribution group in our Exchange 2016 (CU 10 build 1531.3).
I created a new group “test” with address ******@mydomain.it, added some members, but one of them (and only that one, let’s call him “poorguy”) is not receiving emails.

What I’ve checked so far:

  • all groups/distribution lists work correctly, for all other mail recipients, except for poorguy.
  • poorguy has SMTP:******@mydomain.it and SMTP:poorguy@mydomain.local in proxyAddresses attribute. He can send and receive all messages directly from/to his mailbox with no issues.
  • there are no particular policies/restrictions for poorguy. Nothing appears to be different from other users, except from an additional x500 address that comes from a previous migration.
  • I've tried to delete, re-create a new group adding poorguy as the only member, nothing happens (messages just get dropped with no recipient, no NDR)
  • Looking into MSGTRK logs, I found out that problem is with group expansion (RESOLVER.GRP.Expanded; distribution list expanded'): Exchange resolves to all members except from poorguy, like he doesn’t exist. Here is a cleaned up version of relevant lines:

[date],,,,[servername],[serverfqdn],,ROUTING,EXPAND,76940044140619,[testmessageid],1d886c89-fda8-44ba-73a3-08d8385179cf,[@mydomain.it;@mydomain.it;@mydomain.it[poorguy address missing here],'250 2.1.5 RESOLVER.GRP.Expanded; distribution list expanded',10143,0,[@mydomain.it],,[testsubject],[testsender],[testsender],,Incoming,,,,S:DeliveryPriority=Normal;S:AccountForest=[mydomain.local],Email,9ca0bdc2-dfe1-4599-3ab2-08d8385179f3,15.01.1531.010

[date],, [servername],,,CatHandleFail,,AGENT,AGENTINFO,[testmessageid],1d886c89-fda8-44ba-73a3-08d8385179cf,[******@mydomain.it],,10143,1,,,[testsubject], [testsender],[testsender],,Incoming,,[smtpproxyIP],[exchangeIP],S:AMA=SUM|v=0|action=|error=|atch=0;S:AMA=EV|engine=M|v=0|sig=1.321.557.0|name=|file=;S:CompCost=|AMA=0;S:DeliveryPriority=Normal;S:AccountForest=[mydomain.local],Email,86bcdf1d-618f-4368-3ab2-08d8385179f3,15.01.1531.010

Please help me so I can help poorguy :)
Gabriele

Exchange | Exchange Server | Management
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Accepted answer
  1. Gabriware 101 Reputation points
    2020-08-17T17:45:50.44+00:00

    Ok, after many hours of digging and searching I finally found a solution:

    https://community.spiceworks.com/topic/1777632-troubleshooting-exchange-2016-expanding-distribution-groups

    Apparently this is a known bug with no official patches from Microsoft. Quoting from the aforementioned thread:

    “So after almost two weeks of troubleshooting with Microsoft we resolved the issue […] Microsoft then advised that there is a known issue with the Microsoft Exchange Transport service. By default during an Exchange installation the service is created and set to run using the NetworkService logon account. This is how it is supposed to run, however it has been reported to cause issues in Exchange 2016 CU 2. We changed the logon account to LocalSystem account and the delivery to distribution groups started working.”

    So did I, changed Transport service account to LocalSystem, restarted, problem solved immediately.

    The real bad part of all this is the lack of any sign of malfunction: No DNR, no System / Application errors in event logs nor in Exchange logs even with Loglevel = high, nothing wrong with Users/Groups/Rules settings, just that RESOLVER.GRP.Expanded entry with missing recipients.

    As nothing changed after CU17 I suppose the issue has been ignored from MS devs and will remain there forever, so I hope this will be helpful to other admins facing the same situation.

    Thanks to LucasLiu-MSFT and AD-7937 for your support and pointing me to the right direction, I really appreciated.
    Gabriele

    1 person found this answer helpful.

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  1. Lucas Liu-MSFT 6,191 Reputation points
    2020-08-11T05:48:32.1+00:00

    Hi gabriware,
    I agree with andy.
    As far as I know, "CatHandleFail" parameter indicate that this recipient cannot be find when categorize, so please compare the settings and attributes of the problem user and other users.
    Did you create distribution group in EAC? If so, please try to create distribution group by running following command: 

        New-DistributionGroup -Name <> -Members <>

    For more information: New-DistributionGroup .

    1 person found this answer helpful.
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  2. Andy David - MVP 157.8K Reputation points MVP Volunteer Moderator
    2020-08-12T17:29:27.523+00:00

    When was the last time the Exchange Servers were rebooted? Sounds silly, but hung processes can surface issues in weird ways.
    Makes me think that Exchange is having issues connecting to the DCs as far as changes.

    Anything in the event logs that look recent or in an error state? Especially when sending a message to those groups?

    If after a reboot, the problem continues , consider cranking the diags for the MSExchangeTransport\Categorizer to high using set-eventloglevel

    https://learn.microsoft.com/en-us/powershell/module/exchange/set-eventloglevel?view=exchange-ps

    1 person found this answer helpful.
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  3. Andy David - MVP 157.8K Reputation points MVP Volunteer Moderator
    2020-08-04T11:26:39.97+00:00

    Make sure the group is a universal group. Are all the domain controllers GLobal Catalogs and is this a multi-child AD forest or just one domain in the AD forest?
    Also, CU10 is pretty old. I would upgrade to CU17 as soon as possible.

    0 comments
  4. Lucas Liu-MSFT 6,191 Reputation points
    2020-08-05T07:39:09.393+00:00

    Hi gabriware,
    Please try to migrate the problematic user to another database, and then try to send the email again and see if the issue is resolved.

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