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IMCEAEX-_o=NT5_ou=00000000000000000000000000000000

    Question

  • Out of the blue one of our users will not be able to send emails to a MailUser in Outlook, but it will work with OWA

    The error is IMCEAEX-_o=NT5_ou=00000000000000000000000000000000_cn=73495F221CFA124085D6606DD6101CFF@sendingdomain.com

    If I delete the contact completely from Outlook suggested contacts, and any other contact list, the error still remains

    If I create a new Outlook profile, I still get the error.

    I tried the solution in this post, but it did not help, the legacyExchangeDN is populated and correct.

    Another user in the post reported that a corrupt OAB on the Exchange server might be an issue if there are multiple CAS servers/DAG - but I only have a single server with all roles installed

    Anyone any ideas?



    • Edited by PaulNSW Thursday, November 17, 2016 1:37 PM
    Thursday, November 17, 2016 1:31 PM

Answers

  • I suspect that someone deleted the contact and created a new one, but the old legacyExchangeDN remains in the users' nickname cache.  Either:

    1. Delete the entry from the nickname cache.

    2. Add a proxy address of type X500 (no dot) with the following value:

    /o=NT5/ou=00000000000000000000000000000000/cn=73495F221CFA124085D6606DD6101CFF


    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    • Marked as answer by PaulNSW Friday, November 18, 2016 9:03 AM
    Friday, November 18, 2016 3:07 AM
    Moderator

All replies

  • I suspect that someone deleted the contact and created a new one, but the old legacyExchangeDN remains in the users' nickname cache.  Either:

    1. Delete the entry from the nickname cache.

    2. Add a proxy address of type X500 (no dot) with the following value:

    /o=NT5/ou=00000000000000000000000000000000/cn=73495F221CFA124085D6606DD6101CFF


    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    • Marked as answer by PaulNSW Friday, November 18, 2016 9:03 AM
    Friday, November 18, 2016 3:07 AM
    Moderator
  • Hi Paul,

    Except above suggestions, I also recommend you can check if there is the same issue in outlook online mode.

    If online mode works fine, that could be an OAB issue as you mentioned before, because if there are any changes on OAB, they aren't available to users immediately until the OAB generation (OABGen) process has completed, moreover, outlook will automatically update the OAB for Exchange accounts once every 24 hours. Both of these could result in some delay when a outlook client try to get the latest OAB.

    Therefor, we can try to update OAB manually and check if any helps:

    1. Run the following command to update OAB immediately on Exchange server:

    Update-OfflineAddressBook -Identity YourOAB

    2. Update OAB from within Outlook:

    In Outlook 2010, Outlook 2013 and Outlook 2016 tab: Send/Receive> Send/Receive Groups-> Download Address Book…

    Best Regards,


    Niko Cheng
    TechNet Community Support


    Please remember to mark the replies as answers.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Friday, November 18, 2016 9:01 AM
    Moderator
  • Thanks everyone, adding the X500 address seems to have resolved the issue. Emails would send via OWA, so I tried multiple times to regenerate the OAB and download it on Outlook, but unfortunately it made no difference.

    I'm keen to understand why this is happening!

    Seemingly at random a mailuser will stop working, these are new mailusers, created in the last few months. They have never been part of our AD or Exchange before, so I'm not sure how Outlook is getting this crazy X500 address. Any time we had ICMCEAEX errors before, the X500 address matched the format of the OU.

    Is there a better way to create mailusers? When we have an external person working here, we give them an AD account, and set their email address in the AD object. If they need to be part of a mailing list, we create a mailuser for them. They have an email address of user.name.company@external.contact and then their actual email set at the primary SMTP. External.contact is an accepted domain in Exchange.

    Friday, November 18, 2016 9:05 AM
  • The problem is likely that someone deleted the contact and then recreated it.  Outlook users' nickname cache still had the old recipient so when they picked using the autocomplete dropdown, they picked the wrong X.500 address and the message bounced.

    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    Saturday, November 19, 2016 1:49 AM
    Moderator