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ZYTRAX: Greylisting

As part of our anti-spam measures we have implemeted an anti-spam technique known as greylisting. This page is designed to provide information if you have received a message which looks something like that below:

450 <recipient-email-address>: Greylisted, see; from=<sending-email-address> to=<recipient-email-address> proto=ESMTP helo=<mail-server-hostname>

If you are seeing this message for the first time your mail server should automatically treat the 450 code at the beginning of the above message as a temporary failure and retry in which case we will receive the email. You should do nothing in this case.

The policy on our mail servers is to delay accepting mail for a short period and following this delay we then accept, and whitelist, the email source. If your mail server is compliant with the various RFC specifications this policy should not cause any problems. If, however, you suspect your mail server is not compliant or this greylisting service is causing other problems, due the nature of how you send email, please email us at info at zytrax dot com specifying the sending and destination email address and we will ask if the recipient wishes to whitelist your address.

For your information you may wish to read more about the greylisting technique or our page describing the implementation and our reasoning for choosing it.

We regret having to implement this policy. Unfortunately for all of us, too many people abuse the freedom that comes with email.

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Page modified: February 10 2022.