Applies ToOutlook for Microsoft 365 Outlook 2024 Outlook 2021 Outlook 2019 Outlook 2016 New Outlook for Windows

Note: To use encryption, your account must have a qualifying Microsoft 365 business subscription. Compare all Microsoft 365 Plans.

A digital signature attached to an email message offers another layer of security by providing assurance to the recipient that you—not an imposter—signed the contents of the email message. Your digital signature, which includes your certificate and public key, originates from your digital ID. And that digital ID serves as your unique digital mark and signals the recipient that the content hasn't been altered in transit. For additional privacy, you also can encrypt email messages.​​​​​​​

What's the difference between a digital signature and a standard signature?

A digital signature isn't the same as a signature you routinely include with an outgoing message. Anyone can copy an email signature, which essentially is a customizable closing salutation. But a digitally signed message can come only from the owner of the digital ID used to sign it. The digital ID provides verification of the sender's authenticity, thereby helping to prevent message tampering.

Get a digital ID from a certifying authority to use in new Outlook

You will need to obtain a digital ID issued by an independent certification authority. Your organization, however, may have policies that require a different procedure. See your network administrator for more information.

Import or export a digital ID in new Outlook

Before you can import a digital ID, you need to already have the digital ID and know where it is on your device. Use the following instructions to either import or export a digital ID in new Outlook.​​

Import a digital ID

  1. Select Settings > Mail > S/MIME.​​​​​​​

  2. Under Digital IDs (Certificates), select Import to import a digital ID.

  3. Select Browse to locate the digital ID, and enter the password you used when you exported the certificate to this file.

Export a digital ID

  1. To export a digital ID, select Settings > Mail > S/MIME.​​​​​​​

  2. Select Export.

  3. From the Export Digital ID pane, select Browse to locate the ID.

  4. Enter a password to help protect this information. If you don't see any specific certificate in list, it may be because it wasn't marked as Exportable at the time of creation.

Digitally sign a single message

  1. In the message, on the Options tab, in More Options, select Digitally sign this message. ​​​​​​​​​​​​​​If you don't see the Sign Message button, you might not have a digital ID configured to digitally sign messages, or it not active for you.

  2. Compose your message and then send it.

Digitally sign all messages in new Outlook

  1. Select Settings > Mail > S/MIME >​​​​​​​

  2. Select Add a digital signature to all messages I send. If this option isn't available, it means your admin manages this setting on your behalf.

    Note: The settings in new Outlook and Outlook on the web are synchronized. This means that any changes made in new Outlook will be reflected in Outlook on the web and vice versa.​​​​​​​

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See also

Verify the digital signature on a signed email message

​​​​​​​Find digital ID or digital signature services

Open encrypted and protected messages

Send S/MIME or Microsoft Purview encrypted emails in Outlook

Set up Outlook to use S/MIME encryption

Learn about securing and protecting email messages in Outlook​​​​​​​

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