I have been using S/MIME for over a decade. I used PGP a long time ago, but it was way too much to expect others to use. Now that S/MIME is built into major MUA

I have been using S/MIME for over a decade. I used PGP a long time ago, but it was way too much to expect others to use. Now that S/MIME is built into major MUAs, it makes more sense. But one problem I have run into recently is that some correspondents complain that the attached smime.p7s file causes their system to mark my messages as spam. It has made me reconsider using it.