The Exchange Mailbox Merge (Exmerge) utility is an important but sometimes overlooked tool on an Exchange administrator's Swiss army knife. To be honest, I hadn't examined Exmerge recently but decided I needed to take a look at the new version (build 5762) that comes with Exchange 2000 Server Service Pack 2 (SP2). I also had a chance to view this week's Microsoft Exmerge support Webcast (see http://support.microsoft.com/webcasts for information about past and future support Webcasts). To my pleased surprise, Microsoft has greatly enhanced Exmerge. I think you'll find it to be an invaluable tool, and I want to update you about its highlights.
If you're like me, you might have thought of only one or two ways that you can use Exmerge. I've used the tool only as a quick utility for exporting messages to a personal store (PST) file or for moving messages from a mailbox on one server to a mailbox on a different server. The exciting news (for me, at least) is that you can use Exmerge in several everyday scenarios.
Exmerge's potential in disaster-recovery operations is familiar to most of us but is worth another look. After you recover an Exchange 2000 or Exchange Server 5.5 Information Store (IS) to a recovery server, you can use Exmerge to extract messages from the recovered IS and move them to the production store. This capability is especially useful for messages that weren't included in the most recent backup but that exist in the log files that have accumulated since that backup. You can also use Exmerge as a poor man's brick-level backup solution to back up individual mailboxes. To do so, use Exmerge to export Inbox contents to a PST file, then back up individual PST files to tape, thereby making one "brick" of each user's mailbox (assuming you export the entire contents of the mailbox).
Another useful way to employ Exmerge is as a migration tool. Although it wasn't necessarily designed for this purpose, Exmerge can be a great tool for migrating mailboxes and data between Exchange servers during a consolidation or upgrade. There are certain caveats (e.g., loss of single-instance storage, limited support for rules, potential loss of permissions on messages and folders that you move between servers or organizations) to using Exmerge as a migration tool. Still, I've found that many organizations most often use Exmerge as a migration tool, simply because of its ease of use and flexibility. Microsoft uses Exmerge extensively for internal mail-data movement and internal migration purposes. My company (Compaq) also has used Exmerge for migration and mailbox-move purposes for quite some time.
A final use for Exmerge is one that I'd never considered, probably because I hadn't spent enough time with the Exchange 2000 version. This version provides a message-selection feature that lets you filter Exmerge extract operations by subject, string, substring matches, or attachment name. This powerful feature lets Exmerge function as an IS cleaning tool. Suppose that you want to get rid of all a store's messages that have the string "test" in the subject line. Exmerge can find these messages and use an archive switch to remove the messages from the store. Another example of the usefulness of this option is virus removal. If your store is infected with a virus message that contains a specific attachment, Exmerge can find that attachment and clean the messages from your store. One caveat is that the string- and attachment-filtering functions don't support nested messages (i.e., Exmerge can't find a string in or an attachment to a message nested within another message). Despite this minor weakness, the filtering operations are yet another powerful use for the tool.
Exmerge has come a long way from its initial 1997 release with Exchange Server 4.0. In addition to excellent new features, the program has new automation, logging, and command-line capabilities. The Exchange 2000 version is also multithreaded and lets you control the number of worker threads that Exmerge launches. Microsoft Product Support Services (PSS) deserves some kudos for the new Exmerge. My advice is to take a good look at this tool—although hopefully, you've been paying more attention than I have and will be less surprised by the new enhancements.