Digitally sign a message

Digitally signing a message helps protect it from being tampered with while in transit and certifies to the recipient that the message is from you.

To digitally sign your outgoing messages, you need to do the following:

Download and install the S/MIME Control.
Get a digital ID.

Download and install the S/MIME Control

In the Navigation Pane, click Options.
To install the newest version of the control, under E-mail Security, click Download. If an older version of the control is already installed on the computer, you may need to click Re-install to update it.

Important Some computers, especially those available for public use, may not allow you to download this control.

To digitally sign all your outgoing messages, select Add a digital signature to outgoing messages under E-mail Security. Your server administrator may have selected this option by default.
Tip To digitally sign some but not all messages, leave this option unselected. Then, when you create a message or post a message to a public folder, just click Add a digital signature to this message on the toolbar.
Click Save and Close.

Get a digital ID

A digital ID is the electronic equivalent of a passport. It can certify your identity to people you send messages to, help protect your messages from tampering, and encrypt the contents of your messages so that only intended recipients can read them.

Digital IDs can have specific purposes. Some allow you to digitally sign a message but not encrypt its contents, while others allow you to encrypt the contents of a message but not sign it. Some digital IDs have a dual purpose, allowing you to digitally sign and encrypt messages.

If you use Microsoft Office Outlook Web Access on a corporate network, your server administrator may have set up a public key infrastructure that you can get a digital ID from. For more information, contact your server administrator.

If you use Outlook Web Access through an independent service provider, you can get a digital ID from any of several vendors. Some vendors offer free personal digital IDs for signing and encrypting e-mail messages; others charge a nominal yearly fee.

Note Unless you have a smart card or a roaming user profile, you can't carry your digital ID with you or access your digital ID from different computers on a Microsoft Windows network. You must use Outlook or Microsoft Internet Explorer to export your digital ID with your private key to a removable medium, and then import it into the Microsoft Windows certificate store of the user account you plan to use.