Problem migrating Office 365 Mailbox with 99,500+ contacts

I have an end user with 99,500+ contacts including the Recipient Cache.  We're doing an O365 Tenant to Tenant migration.  Every time I try to do a full mailbox migration it stalls with this warning: "The server cannot service this request right now. Try again later. Waiting 5.00 minutes before resuming".  It'll keep saying that forever.  I have a support case open, but I'm trying this avenue as well.  Support asked if there is a folder with a lot of items.  99,500 items is a lot, but we had many other users with many more mail items, and there were no issues with their mailboxes.  I was able to migrate everything else in this mailbox by excluding contacts.  This issue only happens when I try to migrate contacts.  Working on support's theory of too many items in a folder, I split the Contacts folder into sub folders with 23,649 or fewer contacts each (a very tedious process manually using Outlook).  I till keep getting the same "The server cannot service this request right now. Try again later. Waiting 5.00 minutes before resuming" issue.  I could keep splitting contacts into more folders, but I have a feeling that Quest tries to get a total Contact count from all folders and then runs into this issue.  Running "Get-MailboxFolderStatistics -folderscope contacts | select identity, itemsinfolder" returns the count across all folders almost instantly.

Thoughts?  Am I going to have to resort to using Outlook to export these to a PST, and then re-import them?  That'll be disappointing.



  • I worked through this issue. Once I further split up the contacts so no folder had more than about 16,000 contacts, the migration succeeded. Hopefully no one else out there has 16,000+ contacts in a folder, but now you'll know how to work around this issue if you do. I also hope Quest adds this to the documentation.

  • Hello Alex,

    Thank you for posting to the On Demand Migration (ODM) forum. I understand you were experiencing issues migrating a mailbox with a large number of contacts. I also understand that you have already been working with Quest Support regarding this issue. I appreciate you bringing this issue to our attention and letting us know how you worked around it. I have picked up your Support Service Request and will bring this issue to the attention of the product team for further investigation. I will provide you with updates from the Service Request.


    Trevor Taegder
    Senior Technical Support Engineer
    Quest | Support