A legitimate email was rejected by Greylisting and never arrived. What should I do?
First of all, it is suggested to check the ORF logs using the Log Viewer. If the sender was rejected once by Greylisting and never re-attempted the delivery, that indicates a problem on the sender’s side: according to RFC standards, email servers should always re-try the delivery of an email which was rejected temporary by the recipient. You should contact the sender so he/she can investigate this problem. Until this is fixed, you can add the sender to the Greylisting exception list, so future delivery attempts will not be greylisted by ORF. It is also possible that the sender has multiple servers, and each delivery attempt came from a different IP address. You can reduce this problem by enabling the “Accept delivery retries from the same /24 subnet” and/or by adding the sender to the Greylisting exception list.
