Version:           1.6.82 (using KDE 3.2.92 (3.3 beta2), compiled sources)
Compiler:          gcc version 3.3.4 20040623 (Gentoo Linux 3.3.4-r1, ssp-3.3.2-2, pie-8.7.6)
OS:                Linux (i686) release 2.6.7-gentoo-r11

It would be very nice to be able to store some addidional information with an email message.

When e.g. an email asks for payment for something you could write a little note and save it with the message when you did the payment, so you need not remember whether you already acted upon that mail.

You can see whether you already replied to an e-mail but it would be so nice if you could save a little (KNotes-like, maybe) note with a message, that would display when the message is displayed.