I could not find any options in the web interface of Gmail.

All I could find was a Firefox plugin to use S/MIME with Gmail, but it seems to be outdated.


There is Penango - https://www.penango.com/products - which seems to have a free edition for GMail. I looked into it a while back, since as you say, there isn't anything all that up-to-date, but haven't tried it (ended up going with S/MIME in Outlook checking my GMail account).

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  • thanks, that works. Be sure, you use the old standard-compose-message function and you import the root PEM certificate into firefox, if you use cacert at cacert.org/index.php?id=3 – rubo77 Feb 12 '13 at 12:27
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    Now it's only the question, how to read those mails on my android phone too? I guess with k9 mail or so... – rubo77 Feb 12 '13 at 13:24
  • Funny enough, my Chrome doesn't trust their SSL certificate. – simbabque Apr 7 '17 at 18:35
  • Same here, Penagos SSL cert is-- bad – Orphans Nov 14 '17 at 9:26

Use R2Mail2 on Android to read, decrypt, verify, sign and encrypt emails of both PGP, PGP/MIME and S/MIME formats. You can use the IMAP+SMTP interface to Gmail.

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Another option is Fossa Guard - S/MIME extension for Google Chrome browser. S/MIME certificates are free. And it is interoperable with many other mail clients.

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