What term is used as a synonym for Greylisting?

Greylisting is a technique used in email filtering to temporarily reject emails from unknown senders. The purpose of this method is to deter spam and reduce unwanted emails by providing a delay in delivery. When an email from an unfamiliar sender is received, the server responds with a temporary failure, which signals to the sending server that the email should be retried after a certain period. This leads to legitimate mail servers retrying the delivery, while many spam servers, which often send emails only once, will not retry.

The term "deferred" aligns well with this process because it implies that the email delivery is postponed and will be attempted again later. This delay serves as a tactic to differentiate between genuine communication and potential spam, as most legitimate email systems will retry sending the message after a delay.

On the other hand, while "delayed," "pending," and "suspended" might suggest some form of hold or interruption, they do not fully encompass the action of retrying the delivery that is central to greylisting. Thus, "deferred" is the most accurate synonym, as it captures the essence of the temporary rejection followed by a potential follow-up action.