Consider the following scenario:
You receive an email message in a Microsoft Exchange Server 2010 Service Pack 1 (SP1) or a later version environment.
The sender requests a read receipt.
You move this email message to a personal folder file (.pst) or you move the message to another folder in the mailbox.
In this scenario, the following Non-Read Notification (NRN) is sent unexpectedly to the sender:
This issue occurs because a flag that causes the NRN is set incorrectly when you move the email message to a personal folder file.
To resolve this issue, install the following update rollup:
2579150 Description of Update Rollup 4 for Exchange Server 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.