Software :: Changing Back To Apple Mail 3.5 From Microsoft Entourage?

I am trying to change back to the Apple Mail.app 3.5 from Microsoft Entourage and I can't seem to achieve this. I am afraid my Entourage will crash soon because my Database is currently 10.2 GB large. I had to switch 2 years ago from Mail to Entourage, after I lost all my mails because the Mail.app was corrupted. I have had a change of computer although I did migrate my data and was hoping that the mail.app was working better but it is doing strange things like importing folders with no content - although it marks them with the amount of mails located within. It also refuses to import (admittedly) large amounts of mails from Entourage, it doesn't matter if it is just a single folder or several folders. It hoards some old mails in its INBOX which remain there even after I have erased them numerous times. They just keep coming back.

When I use the import option of the mail.app it will not take over all my mails but will save parts of the database or crash when I try to feed it mBox files. I realise my databases are very large but there must be some way to import data from one programme to another. I think somehow my mail.app is broken or it can't handle the huge Entourage database, is there some way I can discover whether this might be the case? I am starting to think I should stick to Entourage because it has been performing faithfully for the past years and I like the appearance more, but because I had database issues under Entourage 2004, I'm afraid my huge database will someday become irreparable. I have a 2.4 Ghz Macbook Pro, 2GB Dram, System 10.5.6, Entourage 2008 and of course the mail.app which I've had to reinstall (with Pacifist) and fix with the new Apple Mail Update that was issued on DEC 23, 2008 (which is supposed to solve stability issues).