Is it true that greylisting works effectively against spam attempts that never retry?

Greylisting is a spam-fighting technique that temporarily rejects unknown incoming emails based on the assumption that legitimate email systems will attempt to resend messages after a short delay, while most spam systems will not. This approach works effectively because many spammers do not have the capability or the incentive to retry sending their email, often leading to their messages being discarded altogether.

By using greylisting, legitimate email senders are usually able to resend their messages successfully, while the spam attempts, which typically do not retry, are effectively blocked. Therefore, the statement that greylisting works effectively against spam attempts that never retry is correct, highlighting the underlying principle of how the method is designed to filter out unwanted emails.