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
    Commented Oct 22, 2017 at 23:27
  • 1
    support.google.com/a/answer/6374496?hl=en confirms: "This feature is only available with G Suite Enterprise."
    – armb
    Commented Nov 14, 2017 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. Commented Jun 24, 2018 at 23:39

2 Answers 2


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.

  • @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. Commented Feb 21, 2013 at 1:08
  • 1
    Penago uses StartCom as a CA, which was rewoked by Google this spring.
    – Orphans
    Commented Nov 14, 2017 at 9:32
  • Possible alternative: fossa.me has a Chrome extension (chrome.google.com/webstore/detail/fossa-guard/…)
    – armb
    Commented Nov 14, 2017 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
    Commented Nov 14, 2017 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
    Commented Nov 14, 2017 at 16:34

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

  • 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 Commented Feb 20, 2013 at 2:32
  • 1
    @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). Commented Jun 24, 2018 at 23:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.