How can I keep a copy of received email on the server?
Follow these steps if you use Outlook 2003.
1. Open Outlook.
2. From the Tools menu select E-mail Accounts...
3. Select the radiobutton next to View or change e-mail account and click Next.
4. Next select More Settings...
5. Select the Advanced tab...
6. Check "Leave mail on server".
In Thunderbird, it is in Tools > Account Settings > __ > Server Settings > Leave Messages on Server.