Thunderbird is the email client that goes with Firebird (browser). Firebird is still only on version 0.6, coming up to 0.7. but it is still waaay better than Netscape, or mozilla, IMHO.
However you should also try Opera or MyIE2 (which dresses up IE) (both also tabbed browsers).
I am using all three at the moment..though mostly Opera & MyIE2.
Try them..it all depends on personal preference.