Send secure email in Outlook using digital signature

Send secure email in Outlook by using a digital signature

Digitally signing an email in Outlook is not the same as adding your text or graphical signature at the end of outgoing messages. An email message signature is simply your customized closing salutation that anyone can copy or mimic.

An Outlook digital signature is a different matter - it adds your unique digital mark to the message. By signing an email with a digital signature, you include your certificate and public key associated with your digital ID (signing certificate). In this way, you prove to the recipient that the message comes from a trusted sender and that its content is intact.

To be able to send secure Outlook emails using a digital signature, you need two basic things:

• Digital ID (email certificate). See where and how you can get a digital ID.
• Set up the signing certificate in Outlook. In the previous article, we also discussed how you can set up the encryption certificate in Outlook. To configure the signing certificate, you perform exactly the same steps with the only difference that you choose to add a Signing certificate instead of Encryption certificate.

Though, if your digital ID is valid both for email encryption and digital signing (and most of email certificates are), it does not really matter which option you choose, both certificates will get configured anyway.

How to sign a single Outlook email with a digital signature

With your digital signing certificate in place, proceed with the following steps.

In a message you are composing or replying to, go to the Options tab > Permission group and click the Sign button.

If you don't see the Sign button, then do as follows:

1. Head over to Options tab > More Options group and click the little downward arrow icon (Options Dialog Box Launcher) in the lower corner.
   
2. Click the Security Settings button and check Add digital signature to this message.
   
3. Click OK to close the dialog and send the email as usual by clicking the Send button.

How to digitally sign all emails messages you send in Outlook

1. In your Outlook, open the Trust Center dialog: go to the File tab > Options > Trust Center and click the Trust Center Settings button.
   
2. Switch to the E-mail Security tab and select the Add digital signature to outgoing messages under Encrypted Mail.
   
3. You can select one of the additional options, when applicable:
   • Select Send clear text signed message when sending signed messages if you want the recipients that don't have S/MIME security to be able to read the messages you send. This check box is selected by default.
   • Check Request S/MIME receipt for all S/MIME signed messages if you wish to verify that your digitally signed email message has been received unchanged by the intended recipients. When you select this option, the verification information will be sent to you in a separate message.
   • If you have several signing certificates, you can choose a proper digital ID by clicking the Settings button.
4. Click OK to close every open dialog box.

   Note. If you send sensitive or strictly confidential information, then you may also want to encrypt the email to ensure the complete privacy.

Other ways to send secure email in Outlook

Admittedly, email encryption and Outlook digital signature are the most common methods of sending secure emails in Outlook and other email clients. However, your choices are not limited to these two options and a few more email protection means are available to you:

• Encrypting email connections with SSL or TLS
• Sending password protected zip files