Grey List auto response not sent

[sillyme]

I activated the Greylist yesterday and it seems to be working well. The only problem is that no one is getting the auto response messge. I kept all the defaults except I changed the fail time to 1 Min.

Is this a problem or does the allow time have to expire before the response is sent?

Thanks

[Code Crafters]

Grey listing works by temporarily refusing mail from an unrecognised IP and expecting the IP to resend in a normal fashion for redelivery in order to be accepted. This is effective as many SPAM clients don't follow this standard procedure. For example, if the settings Temporary Fail Time (mins) and Temporary Allow Time (mins) are the default values of 60 mins and 180 mins respectively then mail will only be accepted from the IP between 1 hour and 3 hours after the first temporary mail refusal. If the IP sends in this time period, the IP is added to the Grey List Safe IPs and all mail from that IP is accepted by grey listing after that. If the IP resends mail within the Life Time (days) then the time to expire is reset. If it doesn't resend within this period its safe IP listing expires and the process starts again. This is an extremely effective SPAM filter and second only to Bayesian filtering which requires training to reach a very high (up to 99.5%) SPAM blocking rate. Grey listing can achieve around 90% SPAM blocking with very low false positives.

If your allow time window is between 1 minute and 3 hours then any mail in this window will safe list the IP meaning that all mail from then on will be accepted providing mail is sent again within the life time of the safe listed IP.

[sillyme]

I have seen that to be case. But no one I have checked with or in my test has the auto response message been recieved. (temporary mail refusal, plesae try again shortly)

[MikeG]

I think that the "Please try later" message is more like an instruction sent to the sender's server to tell it to try later, not an actual email sent to the original composer. The original sender doesn't need to be told anything, as their server should automatically try to re-deliver the message.

[sillyme]

I just thought it should go to the sender or does that cause problems. I have seen the grey list feature of other product reply to sender.

[MikeG]

If the sender got a reply back saying "Please try later", they'd probably try to re-send the email. I'm guessing that this would then mean that you'd have TWO emails trying to get through the system, not just the original one. The second one could cause another "Please try later" message, and so on...

[Code Crafters]

MikeG is right, this is just an SMTP transaction reject message not an email. The sending mail server should retry delivery for a temporary delivery fail error causing it to eventaully arrive in the correct grey listing delivery period and then on be white listed.

[sillyme]

I agree with you those points. Problem I had was after activating the grey list a couple clients started complaining that mail was not making it in. After several hours of tracing, calling etc.. (lol) turned out that the problem was an old secondary MX record in the customers DNS. When my server rejected the initial email it went to a backup sever (somewhere) which had no idea what to do with it so it returned it to the sender. Once I got the customers to update their DNS all appeared to work well.

Thanks

Bob