The email is off an SEO company. This is one of the many tactics which they use to boost their clients website rankings without making them look suspicious to the search engines.

Another method they use, is that they provide free content to web masters on the condition that the content contains a couple of links - some to the site they want to link to - and others to authority sites to make the content look authentic. They go as far as even paying the website owners to place the article on their website.