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Greylisting: Solution for Getting Rid of Spam Email

Greylisting is an effective as well as widely used technique for ensuring protection against spam emails. It is a method that makes sure that the users of email service remain protected against spam emails which never get delivered to them.

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Greylisting: Solution for Getting Rid of Spam Email

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  1. Greylisting Solution for Getting Rid of Spam Email

  2. Table of Contents • Email • Web Server • Web Hosting • Greylisting • Email Delivery Process • How Greylisting Functions? • How Greylisting Functions (Continued) • Advantages of Greylisting • Challenges Encountered by Greylisting

  3. Email • Email (Electronic mail) refers to a message (mail) that gets transmitted and distributed electronically, via a network, among people that are using electronic devices. • It operates over the Internet. The current email systems function on a store-and-forward model. Messages are accepted, delivered, forwarded and stored by email servers. The electronic devices of the users of this service need to connect to a mail server or a webmail interface for the purpose of receiving and sending messages and for downloading.

  4. Web Server YELLOW • A web server’s main function is to store, process and eventually deliver web contents and/or web resources to its clients. A web server refers to a server software or to a system that has one or more computers that run this software and which are able to satisfy client HTTP requests over the Internet and also over private LANs and WANs. It manages client HTTP requests with regard to web resources that are related to one or multiple of its configured/served websites.

  5. Web Hosting • Web servers are provided in web hosting by web hosting service providers to their client website owners for the purpose of storing the files of their websites. Web hosting companies also provide the services and the technologies that aid in processing and delivering web contents and or web resources of their clients. • When these companies provide excellent service, these establish themselves as the “Best Website Hosting Company” or as the “Best Windows Hosting Company” or as the “Top Cloud Hosting Company”.

  6. Greylisting Greylisting defends email users against spam. When greylisting is used by a mail transfer agent (MTA), then any email that is from a sender that isn’t recognized by the MTA will be rejected temporarily. In the event that the mail is licit, the originating server will retry, post having delayed it for some time. When enough time has lapsed, this email will get accepted. Greylisting is an effective measure that is used against mass email tools that are used by spammers which don’t queue or retry mail delivery, as is normal with regard to a legit mail transport agent. When delivery is delayed, real-time blackhole lists and other similar lists get the time that is needed to identify as well as flag the spam source. Hence, there is more likelihood of these subsequent attempts’ detection as spam by other mechanisms than there was prior to the delay that had been caused by greylisting.

  7. Email Delivery Process The Simple Mail Transfer Protocol (SMTP) is used for the purpose of transferring an email from a sender to a recipient. An email that has been sent over the internet will follow the path that is described below. An email is composed by the sender with his MUA (Mail User Agent). This can be an email application that is locally installed or a webmail interface. The Mail User Agent sends the email by establishing an SMTP connection with the Mail Transfer Agent (MTA) of the sender. This is a software on the SMTP server which receives and forwards mails. The email is forwarded by the sender’s Mail Transfer Agent to the Mail Transfer Agent of the recipient. If the email is accepted by the agent, it gets delivered to the inbox of the recipient. If the recipient’s local inbox is synchronized by using the IMAP or POP3 protocol, the email gets displayed as a new message.

  8. How Greylisting Functions? Greylisting occurs in the 3rd step of the email delivery process. This is when the Mail Transfer Agent of the recipient receives the email. The receiving MTA requires the following data prior to accepting an email. The sending mail server’s IP address The email address of the sender, via the SMTP command “MAIL FROM” The email address of the recipient, via the SMTP command “RCPT TO” The above-mentioned data that is also referred to as the “envelope data” is recorded in a list for each incoming email, by the Mail Transfer Agent.

  9. 1-800-123 -8156 Whoa! That’s a big number, aren’t you proud?

  10. How Greylisting Functions (Continued) The Mail Transfer Agent will reject an email initially, in the event that a set of envelope data is encountered by it for the first time. An error code is returned at this stage which indicates that a technical problem has taken place. The sending MTA is prompted to send that particular email again after a specified waiting period. This time when an attempt is made to deliver the email again, the envelope data would be present in the greylist and the email would get delivered. A sending Mail Transfer Agent that is not legitimate will usually not retry. As there isn’t any more attempt at delivering the email, the spam email doesn’t get delivered at all. This is how the spam protection function of greylisting works to get rid of spam emails and the annoyance caused by such mails.

  11. Advantages of Greylisting • There are many advantages of greylisting which are mentioned below, in no particular order. • It reduces spam substantially • It is turned on automatically (server wide) • It doesn’t require any configuration by the user • The time delay involved in it, aids in blacklisting malicious senders • Time delays protect against new unidentified malware • It uses fewer resources when compared to most spam filters • It provides significant support to mail servers globally

  12. Challenges Encountered by Greylisting The sending SMTP server’s IP address must not change. In the event that the sender’s SMTP server’s IP address changes, the incoming email to the recipient’s SMTP server will be identified as unknown. This will greylist the particular email. Mail delivery might fail when the sending mail server has been implemented or configured incorrectly. If the sender’s Mail Transfer Agent does not comply with the request to resend the email, the mail won’t be delivered. It can be circumvented by spammers by using a significant amount of resources. Spammers can send their emails multiple times to bypass greylisting but this requires a lot of logistical effort which is not worth undertaking.

  13. Thanks! ANY QUESTIONS? You can find me at: www.htshosting.org support@htshosting.org

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