Howto Block Entire TLDs in Postfix
Blocking or blacklisting entire Top Level Domains (TLDs) in Postfix mail server may have a big impact to reduce spam, phishing, and other unwanted emails. Dependent on the use case of your systems it is a valid and effective solution. The only drawback is, to monitor your email traffic and check, whether valid emails from blocked TLDs are sent to your systems. Blocking a whole TLD is mostly a temporary thing, as the bad guys move on if the domains on a specific TLD are not usable for their cases.