This white paper presents issues related to running different versions of Microsoft Outlook for manager/delegate pairs (for example, Microsoft Office Outlook 2003 and Microsoft Office Outlook 2007). The paper provides a statement from the Microsoft Outlook product team on the issue, and discusses general issues, customer-reported issues, and calendar risk areas for this scenario.

The text in the Microsoft Knowledge Base (KB) article (http://support.microsoft.com/kb/924470) is written specifically to discourage long-term cross-version solutions. For example, setting up an organizational unit of delegates on Microsoft Office Outlook 2003, and then upgrading the rest of the company including managers to Microsoft Office Outlook 2007 is discouraged. When planning to run for long periods of time with mixed versions of Outlook accessing the same Microsoft Exchange mailboxes (as in the manager/delegate scenario), customers can report inconsistencies. To minimize these inconsistencies, upgrading manager/delegate pairs together where possible is recommended.

Unfortunately, the cause of these inconsistencies has proven to be extremely difficult to track down. They are often complex timing issues related to being temporarily offline, using various devices to update calendars, using add-in solutions on mixed versions of Outlook, and subtle differences between the code of Outlook 2003 and Outlook 2007. Combining all of these update semantics together and aiming them at important mailboxes like manager/delegate mailboxes can, from time to time, result in calendar inconsistencies.

The Microsoft Office Outlook product team is aware of this, and has worked very hard for the Outlook 2007 Service Pack 2 (SP2) release to dramatically reduce these inconsistencies. The calendar reliability work incorporated into the SP2 release was the result of many man-years of work. Unfortunately, the code base between 2007 and 2003 is too different to take these calendar reliability fixes back to 2003, and would require significant re-engineering and risk. The best way to get the improvements of the calendar reliability in Outlook 2007 SP2 is to run Outlook 2007 SP2.

Microsoft understands that corporate environments cannot be upgraded overnight. Many of our customers will run with mixed versions for extended periods of time during upgrades. This is a normal upgrade process, and in no way is the product team saying that an upgrade cannot be performed without simultaneously upgrading all manager/delegate pairs in a single sweep. However, targeting manager/delegate pairs to be upgraded in close proximity will reduce the possibility of encountering calendar inconsistencies. Should you run into inconsistencies during your upgrade, usually the simplest way to address them is to upgrade both manager and delegate to the same Outlook version. Investigating the inconsistencies with mixed versions is often a time-consuming and somewhat painful experience for our customers. Where upgrading will nearly always resolve the issue faster, we have found with experience that an issue that is resolved significantly faster is often favored by our customers.

About this document

This document focuses on the scenario of upgrading a manager to Outlook 2007 while the delegate remains on Outlook 2003. If the delegates are upgraded to Outlook 2007 and the manager remains at Outlook 2003, there is a benefit that the delegate uses all the improvements for Outlook 2007 that are covered in the following sections. However, this still remains an untested scenario.

Download details Using different versions of Outlook for manager-delegate pairs (White paper)

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