This page is about Multipurpose Internet Mail Extensions (MIME) Security with PGP (PGP/MIME) or SMTP (S/MIME).
Originally, I had PGP/MIME set up but what about if a recipient does not have PGP/MIME set up on their end? I started looking into S/MIME and have since started signing my emails.
Since you cannot run PGP/MIME and S/MIME together, you only have a choice of implementing one rather.
Page is currently a work in progress.
What is PGP/MIME (or MIME with PGP)
RFC 3156 illustrates this form of MIME security. RFC 4480 describes the OpenPGP format.
PGP/MIME is integrating PGP (Pretty Good Privacy) with MIME.
There are three content types to implement:
Setting up PGP/MIME
Setting up PGP/MIME is completely dependent on your existing mail setup and environments.
Previously, I have used Apple Mail (being an Apple OS X user) with GPGTools, an installation package used for OS X. But since macOS Sierra, there has been compatibility issues between the two. I have since switched tools and email providers.
What is S/MIME (or MIME with SMTP)
S/MIME is the use of the SMTP protocol with MIME.
RFC 5321 describes the current implementation today of SMTP
S/MIME makes the use of an SSL email certificated issues from a universally trusted authority. There are various authorities out there that offers free certificates.
Setting up S/MIME
You will require an SSL email certificate.
Comodo offers free email certificates.
Once you generate a Comodo certificate, you will also need to obtain the cert in PKCS#12 format.
Your mileage may vary. This content is constantly under development and may change at any time.