ReMail works with Gmail and IMAP e-mail accounts, and begins by downloading all your messages. (It’s estimating that it’ll take about seven hours to download about 13,500 messages from my Gmail account via Wi-Fi.) It compresses messages and trips out formatting and graphics, so a boatload of mail doesn’t take that much space: It estimates that those 13,500 messages will occupy about 88MB, which is practically a pittance on my 32GB phone. And reMail says its search is five times faster than Mail’s.

If reMail was a full-blown e-mail client, I’d go bananas over it, and probably use nothing else. But beyond the excellent search, what it offers are basic e-mail features: You can create messages, reply, and forward, but it displays messages in text mode only, and only works in the iPhone’s portrait mode. It also doesn’t support Exchange. Basically, you’re unlikely to use it as your only e-mail client, but for instantaneous searching, it’s an excellent tool. And reMail plays up its usefulness during international travel, when looking up old mail on a server back in the U.S. can cost a fortune in roaming charges.

Apple’s Mail is a good mail client with pretty good search; Google’s Safari-based Gmail for the iPhone is an amazing Web app that’s mostly meant for use when you have Internet access (it does have rudimentary offline capabilities); reMail is excellent search attached to basic mail features. I’d kill for an e-mail client that combined the best features of all three into one app. For now, though, I use both Mail and Gmail–and, as of today, reMail.