I use to use these years ago, but then I stopped. I find nowadays that what the e-mail provider has on the website is good enough.
When I did use em, I use to use Incredimail, it added some nice features to the e-mails.
I use Thunderbird, its an ok program. I really haven't checked out the extra themes and add-ons you can get.
i don't, i just don't like them. i use the gmail interface which i love and does everything i need. plus i like that it stays online so where ever you go it is with you.
I use the bog standard Mail in OS X, it does everything u need.
Used to use thunderbird, the add-ons really make it something special.
I use Outlook Express because it is simple and comes built-in with Windows. I have to send simple text mails most of the times thats why I never bothered to get a fancy one because Outlook Express is great for text emails, also it is very stable.