I have a bat file I use to create packages which I apply to remote/non domain members so I can control their signatures.
The file looks like this:
"P:\Some_Path\adolsign.exe" --signature "P:\Some_Path\offline package\MySignature" --username MyUsername --makepackage --newdefault
The problem I have is that the package DOES NOT set the signature as the default for new messages. Am I doing something wrong? Is this feature even supported?