This is used to reject spam e-mail containing a URL to the top level domains .date or .loan, and can of course be modified to include others. If you feel your users may ever have a legitimate need to be contacted about these domains it would be best to not use this.
Some familiarity with perl compatible regular expressions in postfix will be helpful.
This pattern matches both http and https protocols, and links containing from 1 to 3 subdomains of the TLD (http://3.2.example.com/ or https://example.com/ would match were .com the target).
Insert that line into your custom body checks file and no more spam du jour. Enjoy.