DPM 2010 Synchronisation with Exchange leads to odd error in Exchange Server Log

On each DPM synchronisation the following errors are logged on the exchange server

Unable to update Mailbox SD in the DS. Mailbox Guid: 2ad8687a-a049-4db2-b8c2-86b493495c20. Error Code 0x8004010f 

Unable to update Mailbox SD in the DS. Mailbox Guid: 03be3109-83b4-45da-8695-8f32371cb0bd. Error Code 0x8004010f

Error:0x8004010f translates as NOT_FOUND

the full event is:

Event Type: Warning 
Event Source:   MSExchangeIS 
Event Category: General 
Event ID:   9554 
Date:    02/11/2010 
Time:    15:40:07 
User:    N/A 
Computer:   BMCEX01 
Description: 
Unable to update Mailbox SD in the DS. Mailbox Guid: 2ad8687a-a049-4db2-b8c2-86b493495c20. Error Code 0x8004010f

I've used the adfind tool to try and identify them:

adfind -gc -b "" -binenc -f " msExchMailboxGUID={{GUID:2ad8687a-a049-4db2-b8c2-86b493495c20}}" -dn

But that returns no records.

So how do I determine what is causing the error messages?

And as soon as you ask the question you make the leap that you haven't for days...

Open an exchange powershell... and run:

Get-MailboxStatistics | where-object { $_.DisconnectDate -ne $null } | Select DisplayName,MailboxGuid

and there are my two accounts. I have no need of them and so I can run:

$users = Get-MailboxStatistics | where-object { $_.DisconnectDate -ne $null } | Select DisplayName,MailboxGuid
$users | ForEach { Remove-Mailbox -Database "Mailbox Database" -StoreMailboxIdentity $_.MailboxGuid -confirm:$false }

Luckily I didn't have to think to construct those powershell commands. Once I'd had the inspiration my google-fu got me to this blog.