Delay is a new method of blocking significant amounts of spam at the mail server level, but without resorting to statistical analysis of heavy weights or other heuristic approaches. This method is also called "Greylisting".

Delaying / greylisting is a very powerful feature of ASSP to combat spam; False positive are near or exactly 0. By default there is an embargo time of 5 minutes (default)

What does it mean? How does the DELAYING filter work?

Delaying is a method of blocking significant amounts of spam at the mail server level, but without resorting to heavyweight statistical analysis or other heuristic approaches. This method is also called "Greylisting".

The delay works on the idea that a properly configured SMTP server will always attempt to re-deliver an e-mail message if a soft error occurs.

How exactly does it work?

When someone sends an email to our server (and you or your client have the delay filter enabled), ASSP will return an error 451 (soft failure) requesting again delivery later. If the sending mail server is configured correctly, it will retry to deliver in X number of minutes. (Depends on your configuration). If the sender's mail server waits and resends, the triple (email address, domain, IP) appears in the white list (delay white list) and you will receive the email.

When will you receive the email?

If the mail server is configured correctly, you should receive the email after a minimum of 5 minutes (default embargo time) and a maximum of 28 hours (default timeout). If the Spammer mail server does not retry delivery (and spammers do not usually retry delivery), the email will be rejected after the waiting time (28 hours) and will never receive the spam message.

Can I lose any valid email?

Only if the sender (sender of the mail server) is not configured to retry delivery, the e-mail will be rejected. If the customer can see a valid email message on their delay log page, they can follow the white list of the email with the REPORT button.