Office 365 Migration Issues

Please find a list of migration issues and resolutions that I captured during my last customers migration:-

Flood mitigation on Threat Management Gateway (TMG) -



Issue Resolution
The operation couldn't be performed because object couldn't be found on '' The object has not been replicated to Office 365, check Dirsync error logs, dirsync email errors. Ensure these errors have all been resolved before the users are added to migration list and ensure the object has been sync’d to O365

A large item was encountered: Item (IPM.Note) Subject:"4600562666", Size: 42.07 MB (44,113,161 bytes), Folder:"Inbox

A large item was encountered: Item (IPM.Note) Subject:"Here's My Card", Size: 42.43 MB (44,493,004 bytes), Folder:"Inbox"

A large item was encountered: Item (IPM.Note) Subject:"", Size: 48.49 MB (50,848,177 bytes), Folder:"PRIVATE EMAILS"


ExMerge -

Search-Mailbox – Needs to be a 2010 mailbox

To be able to use the -DeleteContent Parameter you need to have "Mailbox Import Export" permissions. Without these permissions, the parameter -DeleteContent is not available for the Search-Mailbox Command.


1. Create a new Security Group

2. Enter the following command in Exchange Management Shell (replace the Security Group name accordingly):

New-ManagementRoleAssignment -Name "Import Export Support" -SecurityGroup ImportExport -Role "Mailbox Import Export"

*See below for the command to skip large items

Domain is not an accepted domain for your organization Remove all SMTP addresses from mailboxes that are not registered in O365 (or register the domain names)
Target user already has a primary mailbox. Mailbox already migrated User has already been migrated, ensue no users are duplicated
The target mail user doesn't have an SMTP address that matches the target delivery domain '' Add the target domain SMTP ( to all mailboxes before migration (and ensure they have been sync’d to O365)

Warning: Failed to clean up the source mailbox after the move.

Error details: MapiExceptionNotFound: Unable to delete mailbox. (hr=0x8004010f, ec=-2147221233)

The issue occurs when migrated accounts cannot clear homemdb, homemta, msexchhomeservername and msexchguid attributes from the source server and set the TargetAddress on the source side which it is supposed to do after mailbox move completes (flipping of the attributes starts after 95% completion of the move). A script can be created or apply this hotfix -

Pretty much the same issue as large item count

Error: This mailbox exceeded the maximum number of large items that were specified for this request. --> MapiExceptionMaxSubmissionExceeded: IExchangeFastTransferEx.TransferBuffer failed (hr=0x80004005, ec=1242)

Pretty much the same issue as large item count


*new-MoveRequest -identity $_.UserPrincipalName -Remote -RemoteHostName '' -RemoteCredential $cred -TargetDeliveryDomain '' -BadItemLimit 50 -LargeItemLimit 40


If you receive the following error when trying to migrate to O365, the you will need to check that your EWS endpoints are published correctly. 

The call to '' timed out. Error details: The request channel timed out while waiting for a reply after 00:00:00.Increase the timeout value passed to the call to Request or increase the SendTimeout value on the Binding. The time allotted to this operation may have been aportion of a longer timeout. --> The HTTP request to' has exceeded the allotted timeout
of 00:00:00.0010000. The time allotted to this operation may have been a portion of a longer timeout.--> The operation has timed out

Without stating the obvious, there is a timeout issue! I have seen before if you haven’t published EWS correctly to the internet. Ensure when you connect to that you get prompted for authentication from the exchange server and there is no pre-authentication at TMG/UAG for example. Once EWS is published to the internet correctly you should be able to start migrations to O365!


Written by Daniel Kenyon-Smith