My favorite tools

TheBat! - very good mail program. It has a lot of interesting features: mail templates, flexible accounts and folders system, handy keyboard combinations, usefull address book and many other things.

NOBat.ru - inofficial Russian TheBat site

TheBat World - inofficial German TheBat site

AZZ Cardfile - usefull and very simple PIM (Personal Information Manager).

It doesn't have complicated tree folders or popping windows.
Just list of the cards and the filter for them - and I found it very usefull.