gfi mailessentials release email blocked by greylist

keyword: greylist, block list, spam, IP reputation, delivery behavior. Therefore, the required system resources for further spam filtering on mail servers can be greatly saved by blocking most of the spam sessions in time. The forward and reverse DNS lookups are also adopted to further reduce the false-positive rate to under 0.01%. In our experiments with the real-world mail traffic for a month, the method can block 70.29% and 69.21% of the known and possible messages in the spam sessions with greylisting and block listing. The method is implemented on a mail gateway in a senior high school. We design a method of dynamically updating the greylist and block list based on the delivery behavior of spammers to block spam sessions in time. Its weaknesses are the high false-positive rate and a lack of locality. The latter can detect and reject the clients with poor reputation during SMTP sessions by looking up an external blacklist. The former can efficiently reduce the number of spam sessions, but can be easily evaded if spammers retry spam delivery within a period of time. The next section outlines the troubleshooting process to determine the reason behind the actions taken by this filter.1 Blocking Spam Sessions with Greylisting and Block Listing based on Client Behavior Pin-Ren Chiou, Po-Ching Lin, Chun-Ta Li Department of Computer Science and Information Engineering National Chung Cheng University, Chaiyi, Taiwan Abstract Greylisting and real-time block listing are two common mechanisms for spam filtering. There will be scenarios where customers open support requests wanting to understand why the Greylist filter blocked or allowed specific messages against their expectations. Legitimate mail systems typically try to send the email after a few minutes spammers simply ignore such error messages. The Greylist Anti-Spam filter works by temporarily blocking incoming emails received from unknown senders. In this article, you will learn how to determine why the Greylist filter blocked or allowed a message as part of the troubleshooting process involving this Anti-Spam plug-in.

Greylisting is a simple but very effective anti-spam mechanism that works at SMTP level and based on the premise that spammers continuously send emails without checking for error messages. The Greylist Anti-Spam filter is designed to block spam originating from spammers and bulk mailers that do not resend emails on delivery failure.

Gfi mailessentials release email blocked by greylist