
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.

How much does this app cost ? Looks like a promising application, but it lacks push to email. I really want an application that has that feature as i am addicted to it, all thanks to BlackBerry.
The app is free, which makes it pretty cool. However, not having a search function is really stupid. I don’t know why they didn’t include that. Push is also something they shouldn’t have left out.
[...] found a new email client called K-9 Mail the other day, following a little Googling – and it’s [...]
Neat application. However it doesn’t look like there is an option to “download only first XX kb of messages”. If someone sends you a 10mb email – it’s all coming onto your phone!