Hi List Email is sent to multiple recipients.
When for whatever reason, recipients have incompatible settings (one wants spam to be rejected during SMTP Handshake, another one wants spam to be tagged and delivered to his inbox as example).. ...during the 'RCTP TO' phase, we don't yet know what the result of the mail content filter will be, so we reject the recipients with potentially incompatible settings to the first recipient with 452 4.5.3 to force the sending MTA to open a second session for the tempfailed recipients. We tested this with multiple MTA and it looks like MOST do behave as expected and immediately open the next TCP session to re-transmit the soft-failed recipients. I believe we also tested postfix, but now we have found one postfix instance (unfortunately the swiss government) which does not open a new session immediately but waits for the configured backoff time. The swiss government is sending out press releases to large numbers of recipients and all recipients in one domain are aggregated to be sent in one connection - good! Unfortunately our behavior of soft-failing recipients due to incompatible recipient's personal settings is then bound to cause large delays of several hours until all recipients do get the email, which causes complaints. So based on my observation I wonder... Upon receiving a 452 4.5.3 error, what should the sending MTA do? Reconnect immediately and re-try the soft failed recipients as would be done with the usual 'too many recipients' situation? Or is it correct to wait for the backoff timer? Is there an RFC defining the reaction to specific error codes? What is the sending MTA exactly looking at when receiving an error code? Only the first 452? Combination of "452 4.5.3" or even trying to parse the text behind usually 'too many recipients' which we changed this to 'incompatible recipient settings' and this may cause this issue? Mit freundlichen Grüssen -Benoît Panizzon- -- I m p r o W a r e A G - Leiter Commerce Kunden ______________________________________________________ Zurlindenstrasse 29 Tel +41 61 826 93 00 CH-4133 Pratteln Fax +41 61 826 93 01 Schweiz Web http://www.imp.ch ______________________________________________________ _______________________________________________ mailop mailing list mailop@mailop.org https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop
