PGP works fine, but with email, only encrypts the body of the message and attachments.
The fly in the ointment is the severe problem that using standard SMTP to exchange email, the subject and to/from (in fact all the headers) are in plain text rendering a lot of snooping (who are you talking to, how often and what about) completely open.
Email needs re-architecting and probably needs to move away from SMTP altogether to make traffic analysis and web-of-correspondent tracking hard to do. At the same time one might as well incorporate other messaging types to include text, voice and video messaging all in the one encrypted package. At the very least everything needs to be encrypted and not to leak information if someone happens across / intercepts the whole message or its parts.
As far as I'm aware even PGP/GPG encrypted messages will yield up the key ID of the person they are encrypted to, allowing interception to perform at least some analysis of correspondent webs, but there may be an option to turn that off.
Thunderbird and Enigmail work very well and actually take very little effort to set up and understand, if all you care about is confidentiality of the message body. But watch what you put in the subject line!
A root-and-branch look needs to be taken at this, as sticking plaster solutions aren't going to work. PGP is probably an important component but the protocols, key exchange and transport mechanisms need serious work to keep the bastard's noses out of private correspondence. And they aren't going to like it.