Why don't you use email encryption?
bayareaguy: Although I get a lot of email, I don't really send much and most of what I send is that I can't meet $person when they want because of $reason and that I would rather meet at $date.  That sort of thing
isn't really sensitive.That said, I occasionally exchange details that could be covered by an NDA and for those cases I'll just send an OpenSSL encrypted attachment.  Most people I work with don't have a problem with that
and the few that do are easily helped by simply reminding them of the syntax:  % openssl enc -d -aes-256-cbc -in document.pdf.aes256 -out document.pdf

The biggest problem I have is that people rarely think about the sensitivity of things they send to me unless I explicitly remind them to.