I tried out Ximian Evolution today. It’s an email client, actually more a personal information manager, that looks a lot like Outlook, except that Ximian is free, runs on *ix and will probably not get your computer infected with 298374987 different interesting yet unfriendly viruses.
Hey, interestingly, it seems the correct plural is “viruses” and NOT “viri”. If you’re a pedant, dodge this.
In anycase, usually I use mutt which, unlike Evolution, is exclusively text-based and 100% hot-key (shortcut) driven. For example, to compose a mail, I would go “m”, type the address, the subject and the body of the mail, then ctrl-x-s-x-c and finally “y”. The mail is sent in record-time.