What is the purpose of greylisting in email management?

Greylisting is an effective anti-spam technique used in email management that temporarily rejects emails from unknown senders. When an email is received from a new, unrecognized sender, the receiving server will issue a temporary failure notification instead of accepting the message. This is based on the idea that legitimate email servers will automatically retry sending their messages, while spammers often do not reattempt delivery.

As a result, if the sender is genuine, their email will eventually be resent, and the greylisting server will accept it on the second attempt. This method reduces the chances of spam reaching inboxes while allowing valid messages to eventually get through. This process is particularly useful for filtering out unwanted emails without directly blocking them, which is why greylisting operates on a temporary basis rather than outright blocking or permanently rejecting the emails.