Less spam in your inbox with greylisting

Spam, especially junk mail is annoying. Unfortunately, stopping it is not easy. Spammers make money with it, so they are highly creative in ensuring that spam arrives. Fortunately, there are several techniques to prevent your inbox from containing hundreds of spam messages every day.


Most will have heard of the terms whitelisting (allow) and blacklisting (ban). For email there is also a technique called “greylisting”. This is a technique where email from a sending server which has never been seen before is refused on the receiving server.

If the sending mail server shortly thereafter correctly tries to deliver the mail again, the messages are then accepted. This method prevents a lot of spam by keeping mail servers blocked which display “unhealthy behavior”.

There are geographical locations from where a lot of spam is sent, such as Nigeria and Russia, just to name a few. Henceforth emails from these locations end up on the greylist by default.

The disadvantage of this technique is that a significant delay is introduced for email from servers which have never been seen. Therefore, we also ensure that mail servers from known email providers are automatically considered healthy and do not end up on the greylist. Recently we have marked Office356 as healthy.

More information on this topic can be found at:



Richard de Vroede

A perfectionistic Jack-of-all-trades who dedicates all of his passion to his work.