Config file : make default signature

[bledfeet]

Hi,

I need to create specifics signature manually for outlook for all my users.
So I create the files xx.rtf, xx.htm, xx.rtf in root\users\AppData\Roaming\Microsoft\Signatures
The signature appears well in outlook.

However, I need to make it by default for new messages.
Where could I find the config file for this ?
Intead of going to "options > Courrier > Signatures > Choose default signature " ?

Thanks