Email Signature can be sent with a workflow. If you have a workflow and one of the steps is Send Email, replace it with the following 2 steps:
- 1. Create Email, similar to send email but you only create the email, and do not send it yet.(The send functionality is in the next step).
- 2. Add Step and select Email Signature>Add Signature and Send. This step adds the signature at the end of the email created in step one base on the Properties settings as per this image: