Since some clients want capabilities to be described (e.g. KMail complains that it can't determine UIDL support), I implemented the "CAPA" command as per RFC 2449. The capabilities set also includes "pass" (it's identical to NGPopper's).
See http://www.acm.jhu.edu/~trisk/popa3d-1.0-capa.diff -Trisk
