Exchange 2010 - Dismounted database

I came across an issue on Exchange 2007 a while back now. Basically we received a few alerts on SCOM regarding the Hub Transport Service being stopped on an Exchange Server.
So i jumped onto the server in question and came across the following events in the event log.
Event Type: Error
Event Source: ESE
Event Category: Transaction Manager
Event ID: 623
User:  N/A
edgetransport (5612) Transport Mail Database: The version store for this
instance (0) has reached its maximum size of 249Mb. It is likely that a
long-running transaction is preventing cleanup of the version store and
causing it to build up in size. Updates will be rejected until the
long-running transaction has been completely committed or rolled back.
Possible long-running transaction:
SessionId: 0x0000000005217400
Session-context: 0x00000000
Session-context ThreadId: 0x00000000000014F8
Cleanup: 1
Event Type: Error
Event Source: MSExchangeTransport
Event Category: Storage
Event ID: 17017
User:  N/A
Transport Mail Database: Quota exceeded while performing a database
operation. The Microsoft Exchange Transport service is shutting down.
Exception details:
Microsoft.Exchange.Isam.IsamVersionStoreOutOfMemoryException: Version store
out of memory (cleanup already attempted) (-1069)
at Microsoft.Exchange.Isam.?A0x051b51e0.HandleError(Int32 err)
at Microsoft.Exchange.Isam.Interop.MJetSetColumn(MJET_TABLEID tableid,
MJET_COLUMNID columnid, Byte[] data, MJET_GRBIT grbit, MJET_SETINFO setinfo)
position, Byte[] data)
So i started the Hub transport service again and then had a quick look at the mail queue via queue viewer. In The queue viewer i spotted a 250mb e-mail and consequently was just too big for the hub transport to handle and causing the service to stop.
To get his issue fixed i had to get rid of this mail out of the queue, first i tried removing the mail with no NDR, this got rid of the mail, however 20 seconds later it reappeared again.
So what i had to do was recreate the queue, so it basically got rid of all mail that was currently in the queue. The downside to this is that other mail still queuing up on the Hub Transport server will be lost to.
1, Make sure the MS Exchange Transport service is stopped.
2, Rename the following directory “\Program Files\Microsoft\Exchange Server\TransportRoles\data\Queue” to “\Program Files\Microsoft\Exchange Server\TransportRoles\data\Queue_old”
3, Start the MS Exchange Transport service
4, This Should Recreate the Queue folder and the “MS Exchange Transport” will no longer stop.
This Should Resolve Your Issue.