I have a user running Outlook 2007 on Exchange 2003 SP2 who creates a new meeting (meeting organizer). The user sends the meeting request to several users. The recipients receive and accept the meeting request fine as they should. The meeting organizer then updates the meeting and clicks on "Send Update" within the meeting (outlook 2k7 client). The updates do NOT get sent to the recipients. The meeting update gets stuck in the Messages Awaiting Directory Lookup queue. The message is in a retry status. Every hour I get a messing in the Application event log 6004 "The Categorizer is unable to categorize messages due to a retryable error." The meeting update will eventually timeout and generate an NDR. I do have journaling turned on, the mailbox is valid and is configured to forward all mail to an external contact which points to our 3rd party archiving service. Journaling and archiving works for all other mail messages. I only mention this becuase I have read the microsoft articles regarding journaling and the Messages Awaiting Directory Lookup.

Hello, The cause might be: While enumerating the entries under Global Settings\Internet Message Formats, an invalid entry containing a trailing 'dot' causes Exchange to fail and close all connections to Active Directory. This results in Categorizer initialization failures for all Exchange 2003 servers in the Organization. You can try: 1) Remove the offending entry or correct it by removing the trailing 'dot' in the domain name. 2) Replicate your domain controllers using AD Sites and Services or Replmon. 3) Force connections on the Messages Awaiting Directory Lookup queue. Queues should clear. Thanks, Simon

1) I checked my Internet Message formats, and I do not have any domains with a trailing dot. 2) Not sure if I have a AD domain sync issue. 3) when I try to force a connection on that queue, it does not help, messages are still stuck. Thanks,

Hello, Does the issue happen when updating the meeting request in OWA? You can raise the diagnostic level for Categorizer and see if it can provide more details. In addition, please make sure all the Exchange and Outlook client are up to date. For more reference, please refer to the following link to troubleshooting the “messages stuck in 'Messages awaiting directory lookup' queue”: http://blogs.technet.com/b/exchange/archive/2006/06/23/3394347.aspx Thanks, Simon