To assess your best migration options and plan your strategy, ask yourself the following questions:

Can I migrate all my users at once, or do the old and new systems have to coexist for a while?
If you have a relatively small (fewer than 100 users) post office or several small post offices, you can use the techniques I describe in this article to migrate all users at the same time without setting up directory synchronization. When you surpass 100 users, migrating an entire post office at one time becomes difficult because of the time it takes to update software at the client PCs. Directory synchronization requires configuring the MS Mail Connector. You must also consider how to handle existing gateways. See Robert O'Connell, "Migrating MS Mail Gateways to Exchange Server," July 1998, for a discussion of these topics.

What MS Mail client(s) does my organization currently use?
Does your organization use the DOS client, Windows 3.1 client, or Outlook to connect to MS Mail? These clients store mail differently. DOS uses .mbg, .mai, and .att files on the MS Mail post office to store mail, and .nme files for the personal address list. Windows 3.1 MS Mail uses .mmf files, on the post office or on the PC, to store mail and the Personal Address Book (PAB). Outlook can use .pst files to store mail and .pab files to store the PAB.

Where is my organization's mail and schedule data located?
The location of your mail and schedule files affects your migration options. For example, if your organization's .mmf files are in the MMF subdirectory of the MS Mail post office, you need to use the Exchange Migration Wizard to convert the .mmf files. If the .mmf files are on a LAN or a workstation hard disk, you can use Outlook's import function to import the mail to the Exchange server.

After I migrate, where do I want to store mail?
Whether you store mail on the server, the client, or both depends on how your users use the mail system and how you want to manage it. You might end up with a combination storage scheme. For example, corporate desktop users might store their mail on the Exchange server because they access mail only when they are in the office. Traveling laptop users, however, will definitely want to store their mail on their laptops so they can access it any time or anywhere. When you store data on local machines, you need to decide whether to use .pst or .ost files. Use .ost files when you want to keep the mail stored on the Exchange server for recoverability and also require a local copy of mail or public folders. Use .pst files when you don't need to store mail on the Exchange server. Exchange offers several migration options to handle both client and server postmigration data storage.

What scheduling package does my organization use?
Schedule+ 1.0 or 7.0, Outlook, and third-party packages store schedule data differently. Schedule+ 1.0 uses .cal files on the MS Mail post office and the client to store schedule data. Schedule+ 7.0 uses .scd files on the post office and the client. Outlook stores calendar information either on the Exchange server or in a .pst file.

How are my organization's groups set up?
Do you have any groups (distribution lists­DLs) to migrate? Have you implemented cross-post office groups? Use the MS Mail Admin program to print a list of groups for each post office. From the MS Mail Admin program's main menu, select Local-Admin, Group, Print.

If I have shared folders, what are the current permissions? Where are the shared folders stored?
You need permission information to re-create the access controls on the public folders that migrating shared folders will create on the Exchange server. If an organization has shared folders on a PC, the owner must move the folders to the server before conversion.