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What if my email was rejected and greylisting was mentioned as the cause?

This can happen for various reasons:

  • The MTA (mail transfer agent) / email ISP that you use to send email is not RFC 821 compliant. Contact your ISP.
  • The MTA is in some way misconfigured to not automatically retry email messages that gets rejected with the "try later"-message. Maybe it's timing is off and it retries immediately (which it shouldn't). Contact your ISP.
  • The recipient email server has got greylisting misconfigured, ie. an implementation that just doesn't let mails through even on later retries. Or maybe their error message is actually wrong: greylisting was NOT the reason your mail bounced - but something else.

Can you remove me from your blacklist/greylist?

greylisting.org is JUST an information website. We are not responsible for maintaining any specific blacklists/greylists or for maintaining any whitelists.

You need to contact the actual operator of the mail server that rejecter your email and find out it was rejected (maybe they offer a whitelisting feature).

What's with all these "lists"? What's the difference?

What is greylisting?

Greylisting is a new weapon to use against spam in this great war being waged upon it. With this new shielding method, by which you may block out huge amounts of spam, you are sure to please your email clients!

In name, as well as operation, greylisting is related to whitelisting and blacklisting. What happen is that each time a given mailbox receives an email from an unknown contact (ip), that mail is rejected with a "try again later"-message (This happens at the SMTP layer and is transparent to the end user). This, in the short run, means that all mail gets delayed at least until the sender tries again - but this is where spam loses out! Most spam is not sent out using RFC compliant MTAs; the spamming software will not try again later.

But.. spammers adapt!?

Yes they do. But that does not really make greylisting useless. This delay in new sender contacts also gives you a lot of extra power. This may be an hour, but in this hour there is a large chance that the mass mailer/spammer has been identified by the more conventional anti-spam software. Thus, when he retries it, is likely that we will know him for what he really is!

This site

Learn more about greylisting in our articles section. Check up on other peoples implementations for inspiration/source of your own implementation. When doing greylisting one also needs to consider doing some whitelisting. You may also wish to check our links page for more resources.

Latest updates

09/08/10 Added many new implementations, tweaked a lot of other pages as well and updated the design
11/15/09 Added more implementations, articles and more!
05/08/09 Corrected some links, typos and added a bit around the site.
05/18/08 Added some new implementations.
12/27/07 Some implementations updated and added, articles section re-organised a bit and a new major user added.
08/24/07 Minor design change, new implementations and updated the problem MTAs section.
05/26/07 Added a section for problem servers/MTA (mail transfer agents) as well as many more implementations.
[all updates]

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