True or False: Greylisting is effective against the "Fire-and-Forget" method used to send spam.

Greylisting is an email filtering technique that can effectively combat spam, particularly those that employ the "Fire-and-Forget" method. This method involves spammers sending mass emails quickly, without monitoring the success or failure of their transmissions. When a spam email is sent to a server that uses greylisting, the initial message is temporarily rejected based on the sender’s IP address.

The concept behind greylisting relies on the behavior of legitimate email servers, which typically retry sending messages if the first attempt fails. Conversely, many spamming servers will not resend a message once it is rejected by the recipient's server. This disparity in behavior allows greylisting to filter out a significant amount of spam while allowing legitimate emails through, as they are likely to eventually retry the delivery.

Thus, greylisting serves as an effective defense against the "Fire-and-Forget" approach, as it exploits the tendency of spammers to not reattempt sending rejected emails, significantly reducing the volume of spam that reaches users' inboxes.