If you too often encounter unsolicited emails, then greylisting is the right solution for you. In this post, we’ll take a look at what it is and how it can help you reduce the amount of spam you receive.

How does greylisting work?

Greylisting is a method that protects your email account from spam. The Mail Transfer Agent (MTA) uses greylisting to temporarily reject emails sent from an IP address of an unknown sender.

If the message is legitimate and sent via a normal email server configured according to RFC standards, the rejected message will be resent within a few minutes and this time successfully delivered. The message will be added to a secure whitelist, which means that all further messages will be delivered without any time delay. This rule only applies if the messages are sent from the same email server (IP) as the message that was added to the white list.

How does greylisting affect SPAM?

The aim of spammers is to send messages to as many addresses as quickly as possible without the extra financial resources needed to send them through traditional servers. This is why they use inefficient bulk emailing applications that do not follow the RFC standard. In this case, messages are sent only once, rejected by the email server and never received by the recipient.

The impact of greylisting on the desired emails

Greylisting is effective at filtering out unwanted emails, but it also has a partial impact on preferred mail, which can manifest itself in three ways.

Message delay

As rejected messages have to be resent, you will receive messages with a delay, typically between 5 minutes and an hour.

Unreceived messages

In rare cases, you may not receive an email message from a trusted sender. In this case, it is most often the case that the sender does not have a properly configured email server and RFC standard. We recommend that you inform the sender that you have not received their email and that they contact their email service provider.

Delivery from multiple IP addresses

Major email service providers, such as Gmail, send emails from multiple mail servers, which means that resending will be from a different IP address than the original message, which will further prolong the time it takes to receive the message.