RC looks really nifty: I'd like to try it. Unfortunately, until I can get it to talk STARTTLS to my IMAP server, I'm kind of boned.
Same here, I hacked in STARTTLS support in my version, wireshark says it's working, and my mail shows up (sometimes, but that's another issue (
http://trac.roundcube.net/ticket/1485283))
Here's a patch, it probably doesn't work with NON-TLS enabled servers, so don't use this unless you have a server that absolutely requires STARTTLS, or you know what you're doing.
It requires PHP-5.2.X and it doesn't do much error checking, use wireshark yourself to see what's going on.
cd roundcube/program/lib/
wget "this attachment url" -O starttls_rc.diff
patch -p3 --dry-run < starttls_rc.diff
[check for errors]
patch -p3 < starttls_rc.diff