Consider the following scenario:
In a Microsoft Exchange Server 2010 Service Pack 2 (SP2) environment, Update Rollup 2 for Exchange Server 2010 SP2 or a later version update rollup is installed.
You use an Exchange Web Services (EWS)-based application to access an Exchange Server 2010 Mailbox server, such as a BlackBerry mobile device.
You create an email message, and then you save it in a folder such as the Outbox folder.
You send the email message.
In this scenario, you see two duplicate email messages in the Sent Items folder.
This issue occurs because the Exchange store sets different values for the PR_INTERNET_MESSAGE_ID property of an opened message item and a submitted message item. After the EWS-based application synchronizes the message items with the Mailbox server, duplicates of the same email messages but with different PR_INTERNET_MESSAGE_ID properties are displayed in the Sent Items folder.
To resolve this issue, install the following update rollup:
2746164 Description of Update Rollup 6 for Exchange Server 2010 Service Pack 2
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about the PR_INTERNET_MESSAGE_ID property, go to the following Microsoft website:
General information about the PR_INTERNET_MESSAGE_ID propertyFor more information about this issue, click the following article numbers to view the articles in the Microsoft Knowledge Base:
2592398 Email messages in the Sent Items folder have the same PR_INTERNET_MESSAGE_ID property in an Exchange Server 2010 environment
924213 Message id is different for mail which is in Inbox & Sent items