I have an outlook with 2 email addresses. One is an exchangeaccount and one is gmail.

The exchange one uses a S/MIME certificate to sign outgoing emails. The gmail one doesn't use the certificate.

When sending an email from over the gmail account the user needs to manually disable sign (as it seems in Outlook you can't set auto-sign for just one account without add-ins). This however is not a big problem. The big problem comes when this user receive a signed email on his gmailaccount and reply to it. It looks like the email is sent, no errormessage, but in the "send items" all I see is an empty email with the receiver in BCC (not the normal To:). And the receiver don't receive any email.

I created a new profile and added both accounts again to test it, same result.

Any idea what this is and how to solve it?

  • This problem cannot really be solved until Google Mail supports non-hosted (by Google) S/MIME certificates. – Ramhound Aug 17 '17 at 14:59
  • Hmm not sure if we understand us right @Ramhound . I dont use a certificate for the gmail account, only for the exchange account. Also certificated emails can be answered over the webinterface of gmail without a problem. – nbar Aug 17 '17 at 16:04
  • I understand your problem. Google mail doesn't know anything about signed emails which is the reason it behaves the way it does when you attempt to send an email that is signed by your certificate (connected to your other account) as your Google account. I deal with hundreds of signed/encrypted emails daily, I use Outlook, I am more then familiar with the situation you describe. – Ramhound Aug 17 '17 at 16:41
  • @Ramhound Sending via gmail account is no problem (I disable sign to send the email). The problem comes when I want to ANSWER a signed mail (not sign it myself). Hmm anyway, what solution do you use? Other client? Use 2 different clients, one for exchange(with sign) one for other accounts? – nbar Aug 18 '17 at 12:45
  • I don't combine my Google Account and my S/MIME enabled Exchange server account (or simply don't use the Google account to answer a signed email) which again Google doesn't know how to handle – Ramhound Aug 18 '17 at 13:30

There is an issue (appeared not so far ago) with how Goggle handles S/MIME signed messages.

Please check following threads: https://groups.google.com/a/googleproductforums.com/d/msgid/gmail/0daf2520-8d1a-4536-8734-8dd48ef32215%40googleproductforums.com?utm_medium=email&utm_source=footer


Looks like Google somehow post-process such emails in a favor of G Suite accounts.

I use free Fossa Guard extension for Chrome (accompanied by free X.509 certificates) to exchange S/MIME messages in web Gmail.

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