#linux

Gmail + FireGPG

Firefox+Gmail . FF+ZohoMail for the alternative account.

KMail with pop3 Gmail and couple of different mailboxes.

EDIT KMail because it is lightweight, has all the needed features, integrates well with KDE (obviously;-) and it's easy to use.

I only use a client on the phone (Gmail's mobile client); I much prefer to sign on through the browser (Firefox). I don't like tying myself down to a specific computer.

Thunderbird + popfile in imap mode
TB because it appears to be the least sucky.

KMail with dIMAP and POP3, for every account and gmail webmail for main account

Evolution .. just to get calendar contacts and mail in one client .... otherwise i would use thunderbird

Webmail in various forms (gmail, MessengerExpress and a couple of others).

Firefox and Gmail. I mail that works many locations.

Alpine.

I started with Pine back in 1995 (or -96) and used it for many years. Then I experimented with Thunderbird, Evolution, GMail and Mutt, and finally returned to Pine which had meanwhile become Alpine.

Main reason: My Alpine connects to several IMAP mailboxes and I'd hate to maintain several setups (on all the computers that I use) to get access to all of these boxes one login. So, as Alpine runs nicely in a terminal emulator, I just leave it running on a server and connect to it via SSH anytime I want to check my mail.

There's the added benefit that in another GNU Screen window I have an Irssi instance running, that in turn connects via BitlBee to GTalk and MSN. So, one single SSH and I have multiple IMAP mailboxes and multiple IM protocols at hand. (+loads of other stuff in other Screen windows).