I am not able to understand the significance of a spam email I received from the adultsexmeet website, please explain.

Even-though there are a lot of email addresses available on the internet. There is a fair share of them which are discarded. This email from adultsexmeet is a way to check for the "active" email address. In addition, not all of us would check spam emails and click it. So, this would also gather the email addresses of users who click emails like these even if they are suspicious.This shows that they are a good "target" for future spams. In my opinion, this seems to be an efficient method to gather preferable email addresses for future spams.