Using S/MIME or PGP with receiver

Using S/MIME or PGP with receiver

Hi folks,
It is clear how to establish S/MIME or PGP in Zoho Mail.
Could you please share how you use these with receivers of your emails? Do they have already confirgured certificate or PGP key pair? Do you help them configure S/MIME/PGP?
My cusotmers don't have any, so I cannot ecrypt emails with them. It looks like S/MIME or PGP are not useful to have when receivers don't have these.
Let me know.

Kostadin Kostadinov