I read that it is best to quit Entourage when backing it up to avoid corruption of the database file. (See http://blog.entourage.mvps.org/2009/04/quit_all_microsoft_applications_before_backing_up.html#more). That doesn't appear possible or practical given that Time Machine backups take place every hour. Does anyone know how critical it is to quit Entourage before backing up?

"safe" is not how i would describe it, but I would say the risk of total failure is very remote.

On my system, Entourage is hard shutoff (crashes, power outages, force quits) probably a dozen times a year or more. Since I have had office 2004, I have only had entourage complain once about problems, which were fixed when i rebuilt the database (by holding the option key down). All and all I would call it's databasing system fairly robust.

in practice, I rarely ever have a NEED to recover from a backup, because I dont have system failure often. In the event that I do need to recover, odds are even if the backup occurred during a database update I will be fine. If I am not fine, I will rebuild the database, and if that doesn't work, there are hundreds of other points in history I can try.

If I were planning to migrate to a new hard drive using time machine, I would absolutely shut down entourage first, then do a backup, then do the migration. The rest of the time, I feel that the risk of catastrophic failure doesn't even exist next to the possibility that I can have incremental backups of my 4GB mail archive.