Default email signing with OS X Mail
Solution 1:
I have some email accounts that use S/MIME and some that use GPG. When I select to use the email address configured for GPG, GPG email signing is enabled by default. When I select to use the email address configured for S/MIME, the S/MIME email signing is enabled by default.
I had to enable some settings in the GPG preference section of Mail.app, but nothing else.
