Almost all of my emails are signed
You should see email from me either S/MIME encoded and signed with an X.509 certificate issued by Comodo (standardstrack.com, ieee.org, alum.mit.edu) or InCommon (georgetown.edu), or PGP encoded and signed (standardstrack.com, georgetown.edu). Standardstrack.com also uses DKIM. Mail from georgetown.edu has a Google DKIM signature.
Mail I send from my mobile devices may not be signed. It is too much of a hassle even for me to load up the keys. Someday I may get to it.
My PGP public key is on the appropriate page on this site. If you cannot find it, you probably won’t be able to install it on your system, either.