What I wanted was a *full-featured* POP e-mail client to replace the mail client on my computer, as I use POP extensively, use a variety of different computers and needed a "central hub" kind of concept.
I got that, and so much more. I had downloaded Popper previously, but found the functionality lacking (no personalized folders, no customizability, no skinning and not terribly good looking amongst other things). After trying out tons of other clients, I finally found this not-very-written-about client, the _mod version. Well, what a treat it is!
It has full customizable folders, a calendar (which you can actually add dates and appointments to, unlike the original Popper), great preferences (the ability to change the height of the mailbox and text window is great for better fitting the UI to your screen size).
Finally, the program is versatile, and can be limited to one domain/account/etc., be unlimited (like I'm using it for my 6 POP accounts) or somewhere in between.
This was such a great find for me and clearly an incredible piece of engineering: useable, utterly functional, beautiful! Big thanks to WasecaSoft.