When using the "Send To" Microsoft Outlook function from within Microsoft Word, a mandatory signature cannot be used.
The signature is not available and the signature button is not present.
CauseIf a mandatory signature is being used, the "NewSignature" registry entry is changed by Microsoft Outlook in HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\[Versionnumber]\Common\Mailsettings\NewSignature. As a result the signature button will not be available. To use an existing signature the end-user can right click in the signature field and select a different signature.
This is default behaviour of the Microsoft Office products since Microsoft Office 2007 SP2.