It is good Netiquette to include a website URL. Do provide a link to the company website.
Website Netiquette Signatures
All email comes from a domain on the Internet. These domains have names. There is a domain name. A website URL represents a domain by name.
Many people have separate websites and use other domains in addition to the one from which an email is sent and received. Putting a domain or URL in the signature of a email message provides a reference for the information in the email.
Domain address because it adds credibility.