This is an alpha release. While the functionality is sound, the packaging is probably not even beta quality. Compilation of the components written in C has only been tested under Linux.
postconfirm consists of postconfirmd, which is the long-running (daemon) part, and postconfirmc, which is the client part of a client-server program which handles email confirmations. It is intended as a front-end to mailing lists. It provides funcitonality which is a subset of TMDA, but is adapted to high-volume usage and does not have anywhere near all the bells and whistles which TMDA has. On the other hand, since the whitelist lookup is done by the long-running server part, the overhead of doing a verification that a poster has a confirmed address is much smaller than for TMDA. This makes it a factor 1000 or more faster than TMDA in production, with a memory footprint a factor 20 smaller.