What you need to do is to backup the registry files first, it is recommended however it is totally up to you.
Here we go:
1). Go to start menu, type "regedit" and hit Enter.
2). On the "Registry Editor" navigate to:
HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Common\MailSettingsThe numbers I have highlighted in red is the version for Microsoft Office 2013 and below version have different numbers.
3). On the "MailSettings" page, create two "String Value" with the following name:
4). Once you have got those String Values created, you will need to modify them. Right click the new created String Value and select Modify.
5). Add "Email Signature" to the value data. The value data is the signature that you have created on Microsoft Outlook and this will statically assign this to Outlook which signature to use. Do this to "ReplySignature" String value too.
Now go to Microsoft Outlook and see if you can change anything on the Mail Signature Settings!
Alternatively I have wrote down a script for this and just copy the following script to a notepad then Save the file as "yourfilename.reg". Off you go!
Windows Registry Editor Version 5.00