One of the essential elements of SEO is links pointing to your site from other, better websites. Everyone who has a blog with any traffic at all will eventually start getting these emails. So, people who want to build up their SEO reach out to sites asking to publish a guest post with a backlink to their site. They may make all manner of promises about the quality and relevance of the article, but usually, they're not valuable to you. You have two options for dealing with these. The first is to ignore all of them. I'd say 99% of them are from people who build a list of thousands of email addresses and shotgun out identical emails to all of them. They're also likely promoting low-quality sites that aren't worth your consideration. Ignoring them is generally safe. The other option is to check into who the person is and what site they want to mention. Blogger outreach is a legitimate technique, and many high-quality marketers also do it without abusing it. These generally fall through the cracks, though, as we (as managers of these email inboxes) become blind to them.