Mailbox migration times out when going from Exchange OnPrem to O365
When attempting to migrate an onPrem User mailbox from Exchange 2013 to O365, the following error is generated and the migration fails:
The request channel timed out while waiting for a reply after 00:00:00.0012345. 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 a portion of a longer timeout.
This typically happens when the ExchangeGUID property of the mail-enabled user in O365 does not match the ExchangeGUID property of the corresponding on-premises mailbox that you are trying to migrate. The migration will then timeout because it is trying to look up the wrong ExchangeGUID and will never find it.
Set the ExchangeGUID property of the mail-enabled user in Exchange Online (O365) to match the ExchangeGUID property of the corresponding on-premises mailbox, and then retry the move. To do this, follow these steps:
Retrieve the value of the ExchangeGUID property for the on-premises mailbox that you want to move. To do this, open the Exchange Management Shell on the on-premises server, and then run the following command:
Get-Mailbox <MailboxName> | Format-List ExchangeGUID
Make a note of the value. You'll need it later in step 2B.
Connect to Exchange Online by using remote PowerShell. Then, do the following:
A. Determine the value of the ExchangeGUID property of the mail-enabled user in Exchange Online. To do this, run the following command:
Get-MailUser -Identity <UserName> | fl displayname,ExchangeGuid
B. Set the value of the ExchangeGUID property of the mail-enabled user in Exchange Online to match the ExchangeGUID property of the on-premises mailbox. To do this, run the following command:
Set-MailUser -Identity <UserName> -ExchangeGUID <Value Retrieved From Step 1>
Retry the move.
There are other similar issues but I see this one more than any other when it comes to failed migrations, so I am singling it out for the purpose of this article. If this does not address your issue, please refer to TechNet for other possibilities.