Consider the following scenario:

•	You upgrade to Microsoft Exchange Server 2007 Service Pack 1 (SP1) on the Client Access server
•	A user who has a mobile device may try to connect to a mailbox on an Exchange Server 2003-based server.

In this scenario, the user may be unable to synchronize with the mailbox any more. If verbose logging is enabled on the mobile device, the "HTTP 503" error code is logged.

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This problem occurs because the SAMAccountName attribute of the mobile device user matches the Simple Mail Transfer Protocol (SMTP) address of another user on a different mailbox server . The server that is running Exchange Server 2007 SP1 assumes that its SMTP address belongs to another user on another mailbox server. Therefore, the “HTTP 302” error code is returned. The Exchange ActiveSync handler assumes that a mailbox has been recently migrated from Exchange Server 2003 to Exchange Server 2007. Therefore, the handler blocks synchronization until replication is complete. In this scenario, the user can never synchronize with the mailbox.

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Update information

Download and install Update Rollup 2 for Exchange Server 2007 SP1. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

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To work around this problem, change the primary SMTP address on the E-mail Addresses tab of the user account property so that it does not match the SAMAccountName attribute of another user.

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Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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To enable verbose logging on the mobile device, follow these steps:

1.	Open ActiveSync from the mobile device, click Menu, and then click Configure Server.
2.	In the Edit Server Settings window, click Next.
3.	Click Advanced.
4.	In the Event logging field, click Verbose, click Next, and then click Finish.

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