Secure email messages by using a digital signature

By digitally signing an email message, you apply your unique digital mark to the message. The digital signature includes your certificate and public key, which originate from your digital ID. A digitally signed message proves to the recipient that you, not an imposter, signed the contents of the message, and that the contents haven’t been altered in transit. For additional privacy, you can also encrypt email messages.


  • Digitally signing a message isn’t the same as including a text or picture signature in outgoing messages. Anyone can copy an email message signature, which is basically a customizable closing salutation.

  • You must get a digital ID before you can digitally sign an email message.

Digitally sign a single message

  1. In the message, on the Options tab, in the Permission group, click Sign Message.

    I don't see Sign Message

    1. In the message, click Options.

    2. In the More Options group, click the Options Dialog Box Launcher Dialog Box Launcher button on the ribbon in the lower corner.

    3. Click Security Settings, and then select the Add digital signature to this message check box.

    4. Click OK, and then click Close.

    If the Sign Message button isn’t visible, you might not have a digital ID configured to digitally sign messages.

    Install digital signature

    1. On the File menu, click Options > Trust Center > Trust Center Settings > Email Security.

      Click Import/Export to import a digital ID from a file on your computer or find a list of services that issue digital IDs for your use by clicking Get digital IDs.

  2. Compose your message, and then send it.

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Digitally sign all messages

  1. Click the File tab.

  2. Click Options.

  3. Click Trust Center.

  4. Click Trust Center Settings.

  5. On the Email Security tab, under Encrypted Mail, select the Add digital signature to outgoing messages check box.

  6. If available, you can select one of the following options:

    • If you want recipients who don't have S/MIME security to be able to read the message, select the Send clear text signed message when sending signed messages check box. By default, this check box is selected.

    • To verify that your digitally signed message was received unaltered by the intended recipients, select the Request S/MIME receipt for all S/MIME signed messages check box. You can request notification telling you who opened the message and when it was opened, When you send a message that uses an S/MIME return receipt request, this verification information is returned as a message sent to your Inbox.

  7. To change additional settings, such as choosing between multiple certificates to use, click Settings.

  8. Click OK on each open dialog box.

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