I choose to keep emails on the server and only delete them when deleted from trash. In the past I've been bitten - I'd get to Uni and find that my emails are all at home on my PC
It also prevents me from losing emails if something happens to my PC - corruption of the database files for example. It's for these reasons I'd always advocate the "leave on server until removed from trash" method. The Bat! allows me to vary this on a per-folder basis, so I can leave all emails on the server except those marked as spam.
I have a copy of Mailwasher - licensed. It just doesn't work with NTL's email servers - they respond too slowly and MW wrongly interprets this as the POP server not conforming to the RFCs, which is rubbish. There might be a new version out that actually allows the user to configure the server timeout - wouldn't that be a novelty. MW also has pretty poor out-the-box spam features and actually advocates spamming by offering to bounce spam. We all know that spam rarely has a valid FROM: address, so some poor sod receives an email saying that a message they didn't send has bounced. They then hassle tech support or come on here, and we tell them to ignore it - it's some idiot with a copy of MW. Oh and you can report spam so the sending mail servers are blacklisted - so you have loads of people who haven't a clue what they're doing happily blacklisting email servers, totally undermining anti-spam efforts.
I don't like Mailwasher - you'd never know though
