Why Am I Getting a Missing Certificates Error When Sending Encrypted Emails?
Asked by
CuriousCat2021
I've come across a peculiar issue with one of my users. Whenever they try to send an encrypted email, they face an error saying, "Missing Certificates: Valid Certificates weren't found for the recipients listed above. If you encrypt the message, those recipients won't be able to read it." This happens regardless of whether the recipients are internal or external. We're not using an SMIME deployment and are relying on the built-in encryption in Office 365. Here's what I've already checked: the user's Business Premium license is confirmed, I've tested sending from both the new and classic webmail versions with the same outcome, and I've verified that the SMIME settings are unchecked under mail options. I even ran a PowerShell command and found that both UserCertificate and UserSMIMECertificate return as null. I added a registry key to suppress name checks and rebooted, but the problem persists. Additionally, I checked for any mail rules in the Exchange admin center and in Purview policies affecting that user, but found nothing. I haven't tried uninstalling 365 since the issue also occurs in Outlook on the Web. If anyone has suggestions, I'd really appreciate your help!
Answers
To clarify, how are you setting the email to encrypt? Is it a reply or a new message? Make sure you’re seeing the error you mentioned directly in Outlook Web App (OWA) since it might help narrow it down. Also, if you're dealing with a new email, confirming that the encryption options are configured right would also be helpful.
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It sounds like your client may think they need to enable SMIME in Outlook to send encrypted messages. Just so you know, all they need to do is tag the email to encrypt it by going to new mail > options > encrypt > encrypt-only. You should also check and ensure that mail encryption isn't enabled in Outlook settings. Here’s a helpful guide on how to set it up without SMIME: https://support.microsoft.com/en-us/office/set-up-outlook-to-use-s-mime-encryption-2e57e4bd-4cc2-4531-9a39-426e7c873e26
SmartTechie88: That's interesting! I thought the SMIME settings were necessary for encryption. Good to know that just the tag will work!
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CuriousCat2021: It's a new email I'm trying to send, and the error message I get is exactly as mentioned: "Valid Certificates weren't found for the recipients listed above." I'm attaching a screenshot for reference.