From MozillaZine Knowledge Base
- This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).
Thunderbird does not support or use ActiveX. If somebody gets a ActiveX error when opening a message sent using Thunderbird check whether the signature was created using Microsoft Word. You can prevent this problem by using another program such as a HTML editor like NVU to create the HTML signature.