Hi @T. Kujala ,
If the Active Directory attributes you want to add are listed in the table below, you can create a mail flow rule (also known as transport rule) with an action that adds the specified text to email message.
I tried testing in my Exchange 2019 lab environment by adding an HTML disclaimer below, it can automatically populate the information from AD as expected:
For more details about how to create the organization-wide signature using mail flow rules, you may refer to the following document:
Organization-wide disclaimers, signatures, footers, or headers in Exchange Server
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