Consider the following scenario:
You enable journaling in a Microsoft Exchange Server 2010 environment.
The journal mailbox is an external contact.
You send a recurring meeting request. You select Yearly and a certain weekday of a month for the recurrence pattern.
In this scenario, the journal mailbox receives a non-delivery report (NDR) message that contains the following error message:
#550 5.6.0 M2MCVT.StorageError; storage error in content conversion
This issue occurs because a failure occurs in MAPI to MIME conversion when the journal mailbox is an external contact.
To resolve this issue, install the following update rollup:
2891587 Description of Update Rollup 3 for Exchange Server 2010 Service Pack 3
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.