Greylisting

What is meant by Greylisting?

"Greylisting" is a method used to combat spam in email systems. In this method, the delivery of an email is temporarily delayed by rejecting the email and asking the sender to resend the email at a later time. While legitimate email servers will retry sending the email after a certain period, many spam servers will not attempt a resend. Therefore, greylisting can effectively help reduce the influx of spam emails as spammers often do not retry.

Typical functions of software in the "Greylisting" area are:

1. Delayed Email Delivery:

   • Rejecting emails from unknown senders with a temporary delivery delay.
   • Placing the email on a temporary "greylist" and prompting the sender to resend the email at a later time.

2. Whitelisting and Blacklisting:

   • Ability to configure exceptions for trusted senders (whitelist) or known spam sources (blacklist).
   • Emails from whitelisted senders are immediately accepted, while emails from blacklisted senders are permanently rejected.

3. Configurable Time Windows:

   • Ability to adjust the duration of the delivery delay and the time window in which the sender can resend the email.
   • Flexibility to adapt to the specific requirements and tolerance levels of the email system.

4. Logging and Reporting:

   • Logging of rejected emails and delivery attempts for monitoring purposes and troubleshooting.
   • Generation of reports on the effectiveness of greylisting in reducing spam emails and identifying trends and patterns.

5. Integration with Other Anti-Spam Technologies:

   • Integration with other spam filtering methods such as IP reputation, content filtering, and heuristic analysis for comprehensive spam protection.
   • Combining greylisting with other technologies to maximize spam detection rates and minimize false positives.