I have Outlook configured to automatically sign and encrypt (when possible) outgoing messages. When I send mail to my Gmail (for testing, to see how this appears to addressees) I see that Gmail doesn't identify the signature as such, and simply shows it as an attachment.

Is there any way to tell Gmail to check the signatures and even (gasp!) sign outgoing messages?

  • I think they finally added support support.google.com/mail/answer/6330403?hl=en but it's not mentioned there but appears to be only enabled for Gsuite Enterprise clients. – Ereli Oct 22 '17 at 23:27
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    support.google.com/a/answer/6374496?hl=en confirms: "This feature is only available with G Suite Enterprise." – armb Nov 14 '17 at 16:27
  • @armb : step aside, do you think however, the feature would be available outside G suite through the official Gmail Android app ? I couldn’t found how. – user2284570 Jun 24 '18 at 23:39

Check Penango, it's "the successor to Gmail S/MIME". (Edit - Dead link to old index page replaced by download page for version for free Gmail. Support for Google Apps and paid-for Gmail is a pay-for product.)

Penango makes secure e-mail easy to use, simple to manage, and accessible everywhere. We make a suite of web browser extensions that let you send and receive authenticated and encrypted messages directly in your webmail environment.

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  • @AlEverett Thanks Al! I'll +1 Penango now that I've used it for a few days: in the world of S/MIME not much is easy. Penango is easy. – jeffreypriebe Feb 21 '13 at 1:08
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    Penago uses StartCom as a CA, which was rewoked by Google this spring. – Orphans Nov 14 '17 at 9:32
  • Possible alternative: fossa.me has a Chrome extension (chrome.google.com/webstore/detail/fossa-guard/…) – armb Nov 14 '17 at 16:30
  • Penago's web site still uses a StartCom certificate, which is not a good sign, but they don't appear to rely on it for the webmail S/MIME extension; the instructions on penango.com/products/penangoforwebmail suggest you get a free Comodo certificate if you don't already have a certificate. – armb Nov 14 '17 at 16:31
  • "Currently, Penango works on Firefox versions 3-21,24-26, and Internet Explorer versions 6-9, and Penango for Chrome is under development." penango.com/products/requestpenangowebmailforyourbrowser – armb Nov 14 '17 at 16:34

I've been using the GMail S/MIME for Firefox plugin for a while…

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  • This plug-in appears to be old and no longer functional. See armb's link for a plug-in that works as of this writing on FF 18 – jeffreypriebe Feb 20 '13 at 2:32
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    @jeffreypriebe : the problem is fossa guard requires using fossa certificates, no the provided one to me from Globalsign. I cannot use Penago because, through agreement I need to not register anywhere for getting e‑mail encryption (I’m not paid at all in case of breach of agreement). All I can use is an extension or an open source third party program (no server side parts). – user2284570 Jun 24 '18 at 23:37

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