Hello,
We are using sieve filter to redirect incoming mails to an external mailbox (gmail) an we are seeing some forwarded e-mails being rejected by gmail because of duplicate headers.
I think was able to identify the probable cause of the duplicate headers: It seems that when the original message's "Message-ID" is not compliant, pigeonhole acts like if the header is not existing and adds it's own Message-ID.
This result in having two "Message-ID" headers being submitted to the destination mail server.
Original Message-ID: Message-ID: 1883biz_pay_after_purchase:0:0_572392900$ae7ed6e4d53b424c84aaf83b30c507e7
Pigeon hole adds his own Message-ID: Message-ID: <dovecot-sieve-1664386049-21512-0@510faa1ff2d9>
Gmail answer: 550-5.7.1 [94.103.100.17] Our system has detected that this message is not RFC 550-5.7.1 5322 compliant: duplicate headers. To reduce the amount of spam sent 550-5.7.1 to Gmail, this message has been blocked. Please review 550 5.7.1 RFC 5322 specifications for more information.
While I understand the original "Message-ID" seems to be all but compliant with RFCs, shouldn't a "Message-ID" be added only when "Message-ID" is really missing ? When redirecting a message, If the original "Message-ID" exists but is bogus shouldn't it still be forwarded untouched ?
Also, maybe if pigeonhole is adding it's own "Message-ID", shouldn't it remove any previous "Message-ID" to avoid generating duplicate headers ? (but maybe it could break some DKIM stuff?)
Any ideas how to workaround this issue ?
Thanks a lot for your feedbacks!
Sébastien RICCIO SYSTEM ADMINISTRATOR P +41 840 888 888 F +41 840 888 000 M sriccio@swisscenter.com<mailto:sriccio@swisscenter.com>