Reading mbox mail on Thunderbird (FC5)

[Gordon Charrick]

I've set up Thunderbird with 2 different accounts. One is a pop account 
from my ISP, and the other is a regular mbox account for local email.

The pop account works just fine. I get notified when new mail shows up. 
The problem is that I get no notification when I get local email. If I 
select the inbox for the local mail and click the "Get Mail" button, it 
shows up immediately. Under the server settings I have it set to check 
for new mail every 5 minutes but it doesn't seem to work. Anyone else 
see this problem and have a solution?

The reason I need this to work is because I'm using the mailbox alert 
extension to play a different sound when pop mail comes in versus local 
mail.