Sam, et al, Here's a situation that happened recently. I posted to a popular mailing list and courieresmtp logged the following.
Aug 19 20:12:06 shakti courieresmtp: id=000000000027586D.0000000050318EDD.00006F31,from=<[email protected]>,addr=<[email protected]>: 450-4.3.2 Service currently unavailable Aug 19 20:12:06 shakti courieresmtp: id=000000000027586D.0000000050318EDD.00006F31,from=<[email protected]>,addr=<[email protected]>: 450 4.3.2 Contact your postmaster/admin for assistance. Please provide the following information in your problem report: time (A... Aug 19 20:12:06 shakti courieresmtp: id=000000000027586D.0000000050318EDD.00006F31,from=<[email protected]>,addr=<[email protected]>,status: deferred The connecting server at python.org returned a temporary error. Apparently Courier queued this email for redelivery, and the MUA (Evolution) noted the failure and apparently left the problem email in my Outbox. A minute later, the MUA tried again, successfully: Aug 19 20:13:10 shakti courieresmtp: id=00000000002758BD.0000000050318F21.00006FAC,from=<[email protected]>,addr=<[email protected]>: 250 2.0.0 Ok: queued as 3X0cTL2xBFzQM6 Aug 19 20:13:10 shakti courieresmtp: id=00000000002758BD.0000000050318F21.00006FAC,from=<[email protected]>,addr=<[email protected]>,size=4147,success: delivered: mail.python.org [82.94.164.166] Aug 19 20:13:10 shakti courieresmtp: id=00000000002758BD.0000000050318F21.00006FAC,from=<[email protected]>,addr=<[email protected]>,size=4147,status: success Note the different Message ID. Five minutes later, Courier tried, again successfully, to deliver _its_ queued copy of the message. Note that the Message ID is identical to that of the original deferred post. Aug 19 20:17:08 shakti courieresmtp: id=000000000027586D.0000000050318EDD.00006F31,from=<[email protected]>,addr=<[email protected]>: 250 2.0.0 Ok: queued as 3X0cYw1CRlzQ6g Aug 19 20:17:08 shakti courieresmtp: id=000000000027586D.0000000050318EDD.00006F31,from=<[email protected]>,addr=<[email protected]>,size=4147,success: delivered: mail.python.org [82.94.164.166] Aug 19 20:17:08 shakti courieresmtp: id=000000000027586D.0000000050318EDD.00006F31,from=<[email protected]>,addr=<[email protected]>,size=4147,status: success The end result was that although I only posted once, two copies of my post were delivered to the list, and to all list subscribers. I've had some discussion with two of the primary developers of the Mailman list server package, Mark Sapiro and Brad Knowles. Mark replied as follows below. "shakti" is running Courier 0.64.0: "And therein lies the problem. It appears the mail server (shatki) is configured to attempt delivery to the next hop MTA before returning status to the sender. This in itself is not bad and can result in the sender receiving an error status during SMTP rather than the problematic accept the message and later return a failure DSN to the possibly spoofed envelope sender of the message. This can be a good thing. "However, the problem in this case is shatki received a 450 status from python.org and possibly both queued the message for retry and reported the 450 to the sender. This will result in a duplicate if the sender retries the 450. "I think if shatki is going to report the 450 to the sender during SMTP, it should not retry the send itself. "Otherwise, if it is going to retry, it should either report success to the sender and later send a DSN to the envelope sender if delivery ultimately fails or keep the SMTP session with the sender open and only report status when it gets a 2yz or 5yz response from the next hop. Probably only the former is viable as the latter would likely result in the session with the sender timing out before completion." ----- My question is this. If a receiving SMTP server returns a temporary failure, what should Courier's response be? Should it assume that the requesting MUA will queue the post and retry, or should it return success to the MUA and retry from its own queue. Neither alternative seems to be satisfactory. Is the MUA at fault here for queuing the message and retrying? This doesn't seem logical. What's the fix? -- Lindsay Haisley | "Fighting against human creativity is like FMP Computer Services | trying to eradicate dandelions" 512-259-1190 | http://www.fmp.com | -- Pamela Jones ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ courier-users mailing list [email protected] Unsubscribe: https://lists.sourceforge.net/lists/listinfo/courier-users
