Archives are database files created by you that can be accessed by your mail program (Outlook).  Outlook archives are also called “PST files” due to the fact that their names end with the letters “.pst”.  When you create an archive and attach Outlook to it, you can use it to store email messages and content and thereby take it off of the server.  This is mainly used when you have reached a quota limit and need to avoid having your email account stop working.

It is critical that Archives be viewed as point-in-time snapshots of mail, and not as ongoing storage.  What this means is that Microsoft recommends creating archives with dates in them (such as “mail backup 2009-12-10”) and it use it only for mail up to that point and since the last backup.  If you continually add mail on an ongoing basis, it is likely you will eventually exceed the 2GB recommended maximum and could possibly corrupt the database.  If that happens your archive will be lost.

To that end, you could for example create an archive once a year.  Using the example above, you could create a backup called “mail backup 2010-12-10” when the time comes and store all email received between December 11, 2009 and December 10, 2010.