• DNSL
• Email Defense
• GreyList

You came here probably after seeing a email of yours being rejected with a message like this:

   Greylisted for 300 seconds (see http://postmaster.cyberlogic.net/greylist.php)

The mail server generating this error message is using a system called Greylisting to filter spam and viruses. It relies on mail servers behaving according to the standards and usually doesn't require any action by the user. Your emails should only possibly be delayed.

If you see this error message while sending a email, it probably means your mail server does not properly follow the email protocols as defined by the RFC standards specifications. Due to this failure to follow the standards, bounces may be generated from the sending server when they shouldn't.

The best solution is to contact the system administrators of your email server, and have them upgrade it so that it is standards compliant.

What is Greylisting?

Greylisting is a new method of blocking significant amounts of spam at the mail server level, but without resorting to heavyweight statistical analysis or other heuristical (and error-prone) approaches. Consequently, implementations are fairly lightweight, and may even decrease network traffic and processor load on the mail server.

Greylisting relies on the fact that most spam sources do not behave in the same way as "normal" mail systems. Although it is currently very effective by itself, it will perform best when it is used in conjunction with other forms of spam prevention. For a detailed description of the method, see the Evan Harris' Whitepaper.

Who to contact in case of problems?

Contact the Cyberlogic Postmaster at postmaster@cyberlogic.net.