How to digitally sign an email

Question

We have M365 subscription. To enhance mail security, we are planning to add a digital signature to mail. So anyone would send email, it will be digitally signed using user or computer certificate to claim the ID of sender that is from a genuine user, not an imposter. How can we do it? appreciate your help.

Answer 1

You should start from here: https://learn.microsoft.com/en-us/exchange/security-and-compliance/smime-exo/configure-smime-exo

Answer 2

Hi @Mohd Arif ,

Agree with crypt32.

You need to install the S/MIME before you sign the message.

I have done some research, here’s an article for you reference.
https://www.howtogeek.com/665438/how-to-digitally-sign-or-encrypt-emails-in-outlook-online/

Please Note: Since the web sites are not hosted by Microsoft, the links may change without notice. Microsoft does not guarantee the accuracy of this information.

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Answer 3

Hi there,

-On the File tab, click Options >Trust Center.
-Under Microsoft Outlook Trust Center, click Trust Center Settings.
-On the Email Security tab, under Encrypted Mail, select the Add digital signature to outgoing messages check box.

Here is a link for a detailed description of the process that you must follow.

Secure messages by using a digital signature
https://support.microsoft.com/en-us/office/secure-messages-by-using-a-digital-signature-549ca2f1-a68f-4366-85fa-b3f4b5856fc6

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