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Synchronize a Windows Mobile 6 device with multiple Exchange mailboxes

 Table of contents

 Article summary

A Windows Mobile 6 device does not allow you to synchronize either mails, contacts, tasks or calendar data between two or more Exchange mailboxes.

This article describes how to change the behavior and allow full synchronization with two Exchange mailboxes.

Warning: This includes modifying the devices registry. Unintended changes to the registry may render your device completely inoperable.

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 Products to which this information applies

Information in this article applies to all devices running Windows Mobile 6.

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 Detailed problem description

Prior to version 6, Windows Mobile devices, like PDAs and smartphones, can be synchronized with either one or two PCs, using ActiveSync 4.5 or above. This makes it possible to synchronize mails, contacts, tasks and calendar data between two different PCs and thus between two different Exchange mailboxes.

This is true also if using server sync on one side and ActiveSync with Outlook on the other, as well as using ActiveSync with Outlook on both sides.

With Windows Mobile 6, Microsoft introduced a special feature that prevents exactly this. Synchronizing a specific information type (mails, contacts, tasks or calendar data) with two PCs is no longer possible if both PCs have Outlook with an Exchange mailbox connection. It is only possible if only one PC has an Exchange mailbox connection.

Example: Assume you have a PC at home and another at work, and both have Outlook connected to an Exchange mailbox. Your device already has a defined partnership with the PC at home. Mails and contacts are synchronized, tasks and calendar data are not. You may create another partnership with the PC at work. But you will not be able to synchronize mails and contacts with this PC. You may only synchronize tasks and calendar data with at work. The result is that you will not be able to activate synchronization of any data between home and work.

The device will not allow you to activate synchronization of a specific data type with both PCs at the same time. Instead, an error message is displayed saying that you cannot synchronize a specific information type with the second partner because you already do with the first.

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 Reason for this restriction

Synchronizing a specific information type with two PCs at the same time is referred to by Microsoft as "non local cross pollination". With Windows Mobile 6, Microsoft introduced a new registry setting that enables or disables this feature. The key is a REG_DWORD key at the following location:


The default value is "0" which disables the feature and leads to the problem explained above.

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 Explanation for this restriction

It is not easy to explain why Microsoft has introduced this setting. There are two possible explanations:

  1. There may be companies that do not want their company data being stored on private computers or vice-versa.
    This Explanation is not the best, since this feature prevents this only if employees have Outlook and an Exchange mailbox at work AND at home. Well, it is fairly unusual for people to have Exchange at home. If they use Outlook in standalone mode, the feature does not prevent anything.

  2. Microsoft (or their customers) are scared from people who use more than on computer at work, and install an ActiveSync partnership on two of them. Since both use the same Exchange mailbox, this may lead to serious problems including loops and other strange behavior that may affect the whole Exchange server.
    This Explanation sounds more logical, but it still unsure.

However, there is a way to work around this restriction.

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To resolve this issue, you need to change the respective registry key to "1" and perform a soft reset of your device. After that, you may set up synchronization as desired, but only if you do it on the device itself.

You need a registry editor for Windows Mobile 6. We recommend CeRegEditor by mdSoft. This tool does not require installation on the device itself, but only on a PC. And it includes a soft reset function which is very useful.

CeRegEditor can be downloaded here: http://ceregeditor.mdsoft.pl/

If you have a registry editor installed, follow this procedure:

  • You do not have to delete any previously established partnership.

  • Use your registry editor to navigate to the following key (on the PDA's/smartphone's registry, NOT on the PC's registry):
    If you use a PC based registry editor like CeRegEditor, you need to connect your device to the PC first. A partnership is not needed, since the registry editor also works in guest mode. If you use a registry editor that is installed on the device itself, a PC connection is not needed to change the registry.

  • Change the setting "EnableNonLocalCrossPollination" from "0" to "1". No other values are valid. Do not change anything else.

  • Perform a soft reset of the device. If you use CeRegEditor, you can use the built-in soft reset function.

  • After reboot, connect the device to the first PC and activate synchronization of any information type you like.

  • Connect to the second PC.

  • Use your mobile device's "ActiveSync" program to activate synchronization of any information type you like.
    Note: If you try to set this up on the PC, you will still receive the same error message as before.

You are now able to synchronize any information type between both PCs via the device.

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 Article information

Current revision

Article ID BSKB-000003
Revision 1.1a
Last modification 07/18/09 00:51:24 +0200
Keywords windows mobile 6 wm6 synchronize active sync activesync exchange 2 two pcs clients hosts exchange mailbox mailboxes nonlocalcrosspollination calendar contacts tasks mail mails e-mail

Revision history

Revision Changes
1.1a Correction of some minor typographical errors
1.1 Text improvements
1.0 Initial release

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Disclaimer: The information in this article is provided "as is". Use of this information is at your own risk. Bitshift cannot be made responsible for any damage or financial loss that arises from using information from this article.

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