1) it's Open Source, so I can custom build it for my system 2) It has great support for my multiple POP3 E-mail accounts 3) It's Linux native 4) It's relatively bloat free 5) It's pretty easy to use 6) It uses a pretty standard interface with all the common tools and functions easilly accessable 7) Great support for extentions to easilly add functionality 8) Not succeptable to Virii written to exploit Microsoft Outlook (And completely immune to most modern virii under Linux)
some cons: 1) Getting it to behave properly and launch Firefox in my environment is a PITA 2) no good support for RSS feeds 3) requires quite a bit of desktop space to use effectively 4) adding several names from the contact list can be rather tedious if you actually want to respect privacy and use bcc.
We use Eudora at home. Simply because it's a free edition and it's third party to Microsoft so not as much trouble with disgruntled hackers getting into it. I use Outlook at work because we have our own mail server - MS Exchange and outlook is seamless with that server.
I use evolution on my Linux computer because it's simple and lightweight. And very reliable. On my Windows comp. i use Thunderbird, mostly for the same reasons.
At work i use outlook, because we have many own functions integrated to it.. It is actually really good software for work even it's micro$oft. It has many good features the others doesn't, but those features are not needed home... so..