echo 'Hi Alice! Please bring malacpörkölt for dinner!' |
openssl rsautl -encrypt -pubin -inkey alice.pub >message.encrypted

openssl smime her-cert.pem
   -encrypt
   -des3
   -in my-message.txt
   -from 'Your Fullname <you@youraddress.com>'
   -to 'Her Fullname <her@heraddress.com>'
   -subject 'My encrypted reply' |
 sendmail her@heraddress.com

openssl smime
   -sign
   -signer /path/to/your-cert.pem
   -in my-message.txt
   -from 'Your Fullname <you@youraddress.com>'
   -to 'Her Fullname <her@heraddress.com>'
   -subject 'My signed reply' |
 sendmail her@heraddress.com