If you find the default email client on Android a little lacking, you might want to take a stab at K-9 Mail, an open-source app that offers more stability than the on-board client that comes with your G1 handset.  Considered as one of the best email clients for Android, it works with all POP3, IMAP and Exchange accounts.

Whatever email feature you can think of, K9 probably has it.  From our tests, we've only found it lacking on two ends: there is no search facility and it doesn't support Push.  At this day and age, though, those two things are pretty big deals (while I can live without Push, search is a whole other story), so it's a huge minus for the app on that end.

All the usual mail management features work well, with plenty of options, including multiple inboxes, keyboard shortcuts, server-side deletes and more.  It even allows viewing emails in both landscape and portrait mode, although the landscape (oddly enough) is a bit difficult to read.

As a free app, K-9 Mail is a decent alternative to the default Android email interface.  If you can afford to shell out a couple of bucks, though, I'm pretty sure you can find something with a bit more flair.