This technique works, as long as you are very careful. You
must be SURE to be in the correct database before you synchronize.
Do not use the automatic synch feature as it may synch when you are not ready.
You must be sure to drag the emails from the appropriate folder to the InBox before you synchronize. Otherwise you may synchronize an email sync packet in to the wrong database and it will be quite a mess to sort and separate the records out.
You can set up multiple databases, and synchronize one on one with them. You can use Outlook to distinguish synchronization emails coming from certain clients. Each client should have a folder, and the Outlook Rules should be set up so that incoming email from a client goes in to the appropriate folder.
You will need to move the email from one client's folder in to the main Outlook Inbox from which ACT! finds the synchronization email.