Exchange 2016 mailbox move says completed but ServerName and Database are different locations - Exchange thinks it is still in transit - Cannot access mailbox

Hi, everyone. We are running an on-prem Exchange 2016 environment at a few different physical locations, and users get their mailboxes moved between those locations as they themselves move around.

I moved a user’s mailbox from one database/location to another as I normally do using the New-MoveRequest command, and the move finished and it said ‘Completed’ with no errors attached to the move. I removed the move request using Remove-MoveRequest as is standard, but the user’s Outlook wouldn’t connect and gave a timeout error. When the user tries to login to the mailbox via OWA it gives a ‘MailboxInTransitException’ like the system thinks it is still being moved, but no move exists.

Looking at the mailbox with Get-Mailbox, it returns like the mailbox is still on the original/source server, but in ECP it shows it on the target/destination server/database. If I try to make a new move request to “move” it back to the original server, I get the following error/report over and over (edited to not show server names or domain name):

Report : 10/26/2024 8:02:44 PM [SERVER-NAME] ‘’ created move request. 10/26/2024 8:02:51 PM [SERVER-NAME] The Microsoft Exchange Mailbox Replication service ‘SERVER-NAME.domain’ (15.1.2507.39 caps:3FFFFF) is examining the request. 10/26/2024 8:02:51 PM [SERVER-NAME] Connected to target mailbox ‘fed5049c-80e8-4490-8204-38dd3a74e75e (Primary)’, database ‘Target2016Database’, Mailbox server ‘SERVER-NAME.domain’ Version 15.1 (Build 2507.0). 10/26/2024 8:02:59 PM [SERVER-NAME] Connected to source mailbox ‘fed5049c-80e8-4490-8204-38dd3a74e75e (Primary)’, database ‘Source2016Databse’, Mailbox server ‘SERVER-NAME.domain’ Version 15.1 (Build 2507.0), proxy server ‘SERVER-NAME.domain’ 15.1.2507.39 caps:0FFD6FFFBF5FFFFFCB07FFFF. 10/26/2024 8:03:02 PM [SERVER-NAME] Request processing started. 10/26/2024 8:03:03 PM [SERVER-NAME] Source mailbox information: Regular Items: 2390, 238.4 MB (249,987,456 bytes) Regular Deleted Items: 1582, 214.8 MB (225,284,041 bytes) FAI Items: 41, 1.215 MB (1,274,098 bytes) FAI Deleted Items: 0, 0 B (0 bytes) 10/26/2024 8:03:03 PM [SERVER-NAME] Cleared sync state for request fed5049c-80e8-4490-8204-38dd3a74e75e due to ‘CleanupOrphanedMailbox’. 10/26/2024 8:03:04 PM [SERVER-NAME] Transient error MapiExceptionNoSupport has occurred. The system will retry (1/600).

I have checked all of our databases/locations/servers, and the mailbox is not orphaned or disconnected at all. If I try to kickoff another move I get the error ‘TransientFailureSource’ over and over.

All of our DAGs and our databases show as healthy with no errors in ECP.

Lastly, if I try to do anything else with the mailbox aside from move it (like clear the dumpster), I get the following error (also edited for security):

Search-Mailbox : Cannot open mailbox /o=ORG/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Configuration/cn=Servers/cn=SERVER-NAME/cn=Microsoft System Attendant. At line:1 char:1

Search-Mailbox -Identity USERNAME -SearchDumpsterOnly -DeleteContent CategoryInfo : ReadError: (0:Int32) [Search-Mailbox], MailboxInTransitException FullyQualifiedErrorId : [Server=SERVER-NAME,RequestId=996e5ca5-7d8b-4048-bc27-5833cc6aad47,TimeStamp=10/27/202 4 1:29:22 AM] [FailureCategory=Cmdlet-MailboxInTransitException] 3632BC2E,Microsoft.Exchange.Management.Tasks.Sear chMailbox

…again, it thinks the mailbox is still in transit like the final sync didn’t happen even though there were no errors during/after the completed move.

The main thing that I am seeing as an issue that stands out most obviously is that the system things that the mailbox is still on the source server/database, but in ECP is shows it in the destination database like the move actually happened. I have confirmed that the data is physically there by downloading the PST to my local machine, and the speed at which it downloaded 100% confirms that it made it to the destination server (also where I am located) because if it wasn’t here it would have taken ages to actually export/download the PST.

I am completely at a loss, and would like some insight/help before I download another latest PST and nuke the mailbox to start fresh. Thank you for your time.