It's just a patch that fixes the way it handles message-ID's. A carefully crafted email caused it to generate an extra space when listing the emails (through the POP protocol), which caused outlook and many other pop clients to hang/fail. We've been using it the whole time and it works great
I only have experience on FreeBSD, but on that you download the package from DA then pkg_delete the old version of da_vm-pop and the install the new package using pkg_add da_vm-pop3d-1.1.7e