I just installed Enigmail, a GnuGP (free, open source version of PGP encryption) extension that makes it incredibly easy to send encrypted e‑mail through Thunderbird. Install of GnuGP was easy using MacGPG, but I hit one snag in getting to grips with Enigmail. To work, Enigmail needs to know the path to the GnuGP binaries on OSX, and apparently the MacGPG install didn’t add that to my default executables path. Being somewhat of a n00b when it comes to the Terminal in OSX, I couldn’t figure out how to find out the path. Turns out that a really easy way to find this out is to install the GPGPreferences [links to the download] panel on OSX. When you start it up, the GPG executable path is displayed under the General tab. Easy! For what’s worth, the path on my machine is “/usr/local/bin/gpg” but I couldn’t find any documentation anywhere that included this information!
Anyway, I’ve been using Enigmail since overcoming this little foible and it’s phenomenally easy to work with, with tight integration inside Thunderbird that makes it a joy to work.
And if you’re having trouble installing GnuPG on OSX, I highly recommend looking at this site, which has a real treasure trove of easy-to-follow instructions for gimps such as myself.