If you want a nice Outlookesque email client, then take a peek at Evolution. It is easy to setup and could easily be a drop-in-replacement for Outlook.
Alternatively, if you want an Email client that does email, email and email... ie you don't want a calendar, clock, washingmachine as part of your email client then I can recommend Sylpheed. It also does 'news', but that's a different story. It too is easy to setup.
You should check with your ISP for the pop/smtp addresses to use, but as a generalisation they are usually along the lines of:
Incoming = pop3.yourisp.com
Outgoing = mail.yourisp.com
Sometimes it is only pop.yourisp.com, sometimes it is pop3. Try one and if it doesn't work, try the other... and if that doesn't work then ask your isp for details - and do not take 'just click here in outlook' for an answer!
If you were using Hotmail through Outlook then things a much more complicated!
Hope this helps.