I got fed up with gnubiff not supporting TLS, so I whipped up this patch last night. I haven't tested it very much yet, but it works for me. It doesn't yet do POP3 or allow specifying a custom TLS certificate, but this should be easy to add.
This is patched against the latest release, gnubiff 2.2.8, NOT against CVS. It's pretty simple, so it should merge cleanly.
Comments/improvements are most appreciated.