Exchange Server 2007 can be installed into an existing Exchange 2000/2003 (hereafter called Exchange 2003, except where there's something particular about Exchange 2000) organization as one step in the migration process. Once Exchange 2007 has been introduced into the Exchange 2003 organization, the organization is considered to be in a co-existence or "Interop" (interoperability) state so long as both versions are present in the Exchange organization.

While in this co-existence mode, Exchange 2003 and Exchange 2007 each have some management behaviors that you should keep in mind. This blog post will detail some of these behaviors.

Mailbox Management

Exchange 2003 mailbox management is done through the Active Directory Users and Computers (ADUC) snap-in extension for Exchange. Exchange 2007 mailbox management is done through the Exchange 2007 Exchange management shell or the Exchange management console GUI. Separately there is no confusion. However, when you're in a co-existence state, both management tools will be present. Although Exchange 2007 will not install the Exchange extensions for ADUC, any remaining Exchange 2003 servers or "admin-only" installations will still have this snap-in available for use.

So which tools to use on which objects? Here's the easy list to remember:

-           Exchange 2007 mailboxes must be managed with Exchange 2007 management console or shell.

-           Exchange 2007 mailboxes MUST NOT be managed with Exchange 2003 tools. Note that this is not blocked, but mailboxes managed from Exchange 2003 ADUC will not be fully functional.

-           Exchange 2003 mailboxes can be edited or removed with Exchange 2007 tools, but cannot be created by Exchange 2007 tools.

-           Exchange 2003 mailboxes can be managed with Exchange 2003 tools.

-           Both Exchange 2003 and Exchange 2007 mailboxes can be moved (in either direction) with the Exchange 2007 tools. Exchange 2003 move mailbox cannot be used to move mailboxes to or from Exchange 2007 mailbox server.

Recipient Management (contacts, groups, etc)

Since these other recipient objects (contacts, groups, etc) are not tied to a particular server version in the way a mailbox is, these objects can be managed successfully from either side. Because Exchange 2007 tools have knowledge of the full set of Exchange 2007 properties and validation rules, it is recommended to consistently use the Exchange 2007 tools for this recipient management for best results.

The one exception to this rule is Dynamic Distribution Lists (DDL or sometimes called Dynamic Distribution Group, so DDG). Since DDLs created with Exchange 2007 tools store their RecipientFilter in an OPATH format and those created with Exchange 2003 tools store the filter as LDAP, it makes these edits incompatible. Be sure that after you've set a DDL filter through Exchange 2007 you only edit this DDL through Exchange 2007 tools from that point forward.

Global Objects (Address lists, EmailAddressPolicy, etc)

There are also a number of global configuration objects shared between Exchange 2003 and Exchange 2007 when running in a co-existence state. Examples of these objects are: Address Lists, Email Address Policies, Offline Address Book, etc.

These global objects generally follow the pattern that if they are created in Exchange 2003, they can be fully edited only in Exchange 2003 until they are upgraded to Exchange 2007 version. Once upgraded to Exchange 2007 format (and for objects created in Exchange 2007), they can no longer be edited by Exchange 2003 (and Exchange 2003 system manager will actively block you making edits after the object is upgraded).

Also, as mentioned in the "Goodbye RUS" post, you should not configure an Exchange 2007 server to serve as the "Exchange Server" for a Recipient Update Service. Doing so will cause that RUS to cease to function.

Other Miscellaneous Objects

In Exchange 2003 system manager there are a number of other objects that are visible. For instance, the Exchange 2007 administrative and routing groups (and their embedded GUID) are visible to Exchange 2003 while the entire AG/RG concept is hidden in Exchange 2007.

Similarly, the Exchange 2007 server object (and storage groups, databases, protocols, etc) are also visible in Exchange 2003. Where possible, these Exchange 2007 objects are "blocked" from editing through the Exchange 2003 tools. In all cases, you should not use the Exchange 2003 tools to manage Exchange 2007 servers or Exchange 2007 versioned objects.

Some items in the Exchange 2003 are not hidden or blocked, but are simply non-functional. Deprecated items like monitoring administration and Exchange 2003 queue viewer remain visible and will produce an error connecting to the interface if you attempt to access them.

Finally, some items in the Exchange 2003 ESM will remain the appropriate GUI way to manage certain objects until replacement GUI is established in Exchange 2007. Two such items that fit this mold are the Public Folder GUI (which will remain functional and supported, so long as an Exchange 2003 server is the targeted public folder store) and the Address/Details template customization GUI. In both of these cases, the Exchange 2003 GUI is anticipated to be replaced by updated Exchange 2007 GUI at some point in the future.

Exchange 2000 and object blocking

Exchange 2003 ESM automatically includes support for "blocking" edits against Exchange 2007 objects, as described above. Exchange 2000, however, requires a post-SP3 hotfix to provide this same behavior. Although Exchange 2000 SP3 is the prereq'd version required by Exchange 2007 setup, you must make sure that all Exchange 2000 servers and Exchange 2000 admin-tools-only consoles are updated with both Exchange 2000 SP3 and the 6603+ roll-up hotfix – KB.870540 (also known as the August 2004 roll-up hotfix). Note that if this hotfix is not present on an Exchange 2000 admin console used to manage your Exchange 2007 objects, it is possible that Exchange 2007 objects can be modified incorrectly from this legacy console.