Outlook Message ActiveX Object Error

In Microsoft Outlook, when starting an HTML-formatted email message, you are prompted with the following error: One or more ActiveX controls could not be displayed because either: 1) Your current security settings prohibit running ActiveX controls on this page, or 2) You have blocked a publisher of one of the controls.

To resolve, locate the .HTM version of the signature from %APPDATA%\Microsoft\Signatures and open it with Notepad. Remove the following text:

<object classid="clsid:38481807-CA0E-42D2-BF39-B33AF135CC4D" id=ieooui></object>