I've been using Sigsync Office 365 email Signature for many years. I like it. It grabs all of the user data from our Active Directory. We use it for branding, advertising, and disclaimers. It is very reliable and easy to use, I find that from a signature customization perspective, Sigync is far the best. I've been able to set up a single signature for an entire organization. If your comfortable making the signatures in HTML I would recommend that.
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