What term is used as a synonym for Greylisting?

The term "deferred" is used as a synonym for greylisting because greylisting is a temporary email denial technique employed by mail servers to combat spam. When an email is received from an unknown sender, the server will respond with a temporary rejection, essentially deferring the delivery of the message. This approach exploits the behavior of many legitimate mail servers that will attempt to resend the email after a certain interval, while most spam servers will not. Thus, the concept of "deferral" directly aligns with the function and intention behind greylisting, which is to delay email processing as a means of verification and filtration.

The other terms do not accurately capture the mechanism of greylisting. "Delayed" suggests a straightforward slowing down, while "halted" and "suspended" imply a complete stop in action, which does not align with the reinstatement of delivery attempts that occurs in greylisting practices.