Again, many of these offers you'll receive look legit enough. They come complete from a real email address, with a realistic name, a real phone number, and all of the other necessary credentials to look respectable. Sure, they're real people on the other end of the line, but unlike most reputable freelancers in the SEO business, these folks have chosen to use dubious tactics (sending mass emails and spam) to thousands and thousands of people in the hopes that one or two follow up and fall into the trap.