I just checked the email address in our internal Dell Outlook. It is indeed a valid Dell email address. I cannot speak to the specific Dell product or purchased warranty. Contact DELL-Cares agent via Direct Message to ascertain that data.
My Boss received an email from  warranty.dellbusiness.na[NAME].com  saying the warranty on one of the companies smart boards is about to expire. The email looks kind of shotty and I do not trust that is is really from dell. Also the email seems a little off to me. I want to make sure it is legit before advising my boss. 
Your Dell support contract is expiring soon