Hey, Mike,
Aaron is right. Since the campaign you send out actually belongs to Greg, it will have his signature (because he has Add Signature to Emails set to Yes in his profile).
What you can do to "fix" this is either have us change the ownership of that campaign to you (so it adds your signature) or set Greg's Add Signature to Emails option to No and append your signature manually to every campaign e-mail.

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Andy
Technical Support
Real Estate Webmasters | Ordering New Work