I have two Gmail accounts in Outlook, both of which have their respective S/MIME certificates. I have imported these certificated to Trust Center, and created two Security Settings, for each certificate/account.

But, when I try to test encryption by sending an e-mail from one of these accounts to the other, I get the following error message:

"Microsoft Outlook had problems encrypting this message because the following recipients had missing or invalid certificates, or conflicting or unsupported encryption capabilities", followed by the e-mail address of the receiving account.

Does anybody know what's the problem here? It's getting pretty frustrating by now. Thanks.
SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.

You may create the Gmail account contact in Outlook, open the contact click on Certificates, click on Import and import the certificate in Outlook and check if it works as expected.

I hope the above information helps. Let us know if you need further assistance.

Thank you.

SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.

I'm having a similar problem.

Some people I can encrypt and send and receive encrypted emails to and from. Others in my company, I can receive and read their encrypted emails, but get the pop-up box which reads:

"Microsoft Outlook had problems encrypting this message because the following recipients had missing or invalid certificates, or conflicting or unsupported encryption capabilities", followed by the e-mail address of the receiving account.

I have deleted the contact, reloaded their certificates, and everything in between.

I am at my wits end with this problem. Is there an easy fix? Am I overlooking something simple?

Please help!

SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.

I have this exact same problem. Except, my recipient is using a custom e-mail domain rather than a Gmail account.

And here's the weird part. When I try to initiate an encrypted e-mail to this recipient, it fails. But, when I reply to his digitally signed e-mail, encryption works just fine.

I have this person in my Contacts list within Outlook 2016. I've tried deleting and re-adding this person to my contacts list. But, the problem remains.

SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.

To help you get started with your concern, here's a link that might somehow shed some light with the issue. However, this is a part of the workaround. For us to know the issue, please also provide us the following information:

Are you using Microsoft Outlook 2016 client or via Outlook.com?

Were there any changes made prior to the issue?

We'll look forward to your reply.

SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.

Same problem. I have two email accounts set up on the Outlook 2016 client.

Both have certificates installed.

When I send an encrypted mail from the first account to the second one (or vice versa), everything works fine. But when I try encrypting an answer to a (signed) email coming from someone else, "Microsoft Outlook had problems ... "

SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.