Unless it is from the registrar you are using (examples include GoDaddy, Racknine, 1and1 and others) it is probably a misleading email. Make sure you know who your domain name is registered with (or if someone handles that for you, just forward the email to them). Two different things could be occurring.
The first one is the one I see occurring the most often. It is actually a sales offer but disguised as your domain expiring notice. It is from some group that wants you to pay them to increase your SEO score on Google and get a higher ranking when people search for you. If you read their email carefully they say your agreement to get the higher ranking is expiring and that your ranking will fall if not renewed for around $70. Actually, your ranking ruses and falls as Google changes their metrics regularly and tries to penalize people for gaming the system. There are ways to work your ranking better but none can guarantee top unless it is for a special term. For instance, my site, I can pretty much be confident will be at top for “dwight watt”. However, for other stuff searched to find it, the answer is no. It is a misleading ad and I wish authorities could stop it as it has been around years, but they carefully state in smaller print what they are doing that is a sales proposal.
The second one is from other domain registrars who charge a lot more and want you to transfer and renew on them so hey make lots of money. Generally, your domain today should be about $10-$20 per year (there are some specials occasionally) and these ads I usually see want you to renew for a “cheep price” of about $70 per year. That was a good price in 1997 but this is 2017 so do not fall for it.