Looks like nms formmail was packaged for sarge but not for etch.
Provided that you're willing to resolve the dependencies by hand, you should be able to download a sarge package and install it on etch.
Download packages from here.
Install them with dpkg -i $filename. Any dependencies aside from the various bits of nms-cgi can be installed using apt-get as usual.
And as an aside, whenever you meet one of the Debian Cabal, smash him over the head with a heavy blunt implement while screaming USE VERSION NUMBERS INSTEAD OF CUTESY NAMES YOU CRETIN. Because unless you spend far too much time playing with your OS (as opposed to using it) you have no idea what the current version is called, and whether it comes before FluffyBunny or after IckleBabyLamb.