Final answer:
Greylisting is a method used to prevent spam emails by temporarily rejecting them, forcing the sender to resend. It helps reduce the amount of spam in users' inboxes.
Step-by-step explanation:
Greylisting is a method used to prevent spam emails from reaching a recipient's inbox. When an email is received, the server temporarily rejects it by sending a 'soft bounce' error message. The sender is then forced to resend the email, and if it is a legitimate sender, the email will be accepted and delivered to the recipient's inbox. This technique helps to reduce the amount of spam that reaches users' inboxes.