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Hello, </p>
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<p class="MsoNormal" xmlns="http://www.w3.org/TR/REC-html40" style="background-color:rgba(0,0,0,0);margin:0px;">
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.
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<span>I think was able to identify the probable cause of the duplicate headers:</span></p>
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<span>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.</span></p>
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This result in having two "Message-ID" headers being submitted to the destination mail server.
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Original Message-ID: </p>
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Message-ID: 1883biz_pay_after_purchase:0:0_572392900$ae7ed6e4d53b424c84aaf83b30c507e7
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<p class="MsoNormal" xmlns="http://www.w3.org/TR/REC-html40" style="background-color:rgba(0,0,0,0);margin:0px;">
Pigeon hole adds his own Message-ID: </p>
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Message-ID: <dovecot-sieve-1664386049-21512-0@510faa1ff2d9> </p>
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Gmail answer: </p>
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<p class="MsoNormal" xmlns="http://www.w3.org/TR/REC-html40" style="background-color:rgba(0,0,0,0);margin:0px;">
  550-5.7.1 [94.103.100.17]  Our system has detected that this message is not RFC
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  550-5.7.1 5322 compliant: duplicate headers. To reduce the amount of spam sent </p>
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  550-5.7.1 to Gmail, this message has been blocked. Please review </p>
<p class="MsoNormal" xmlns="http://www.w3.org/TR/REC-html40" style="background-color:rgba(0,0,0,0);margin:0px;">
  550 5.7.1  RFC 5322 specifications for more information. </p>
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<p class="MsoNormal" xmlns="http://www.w3.org/TR/REC-html40" style="background-color:rgba(0,0,0,0);margin:0px;">
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 ?
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When redirecting a message, If the original "Message-ID" exists but is bogus shouldn't it still be forwarded untouched ?
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<p class="MsoNormal" xmlns="http://www.w3.org/TR/REC-html40" style="background-color:rgba(0,0,0,0);margin:0px;">
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?)</p>
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Any ideas how to workaround this issue ?</p>
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<p class="MsoNormal" xmlns="http://www.w3.org/TR/REC-html40" style="background-color:rgba(0,0,0,0);margin:0px;">
Thanks a lot for your feedbacks!</p>
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<p class="MsoNormal" xmlns="http://www.w3.org/TR/REC-html40"><b><span lang="EN-US" style="font-size:10.0pt;color:#C00000;
mso-ansi-language:EN-US;mso-fareast-language:#2000">Sébastien RICCIO</span></b><span lang="EN-US"><o:p xmlns:o="urn:schemas-microsoft-com:office:office"></o:p></span></p>
<p class="MsoNormal" xmlns="http://www.w3.org/TR/REC-html40"><b><span lang="EN-US" style="font-size: 10pt;">SYSTEM ADMINISTRATOR</span></b><span lang="EN-US"><o:p xmlns:o="urn:schemas-microsoft-com:office:office"></o:p></span></p>
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mso-ansi-language:EN-US;mso-fareast-language:#2000">P</span></b><span lang="EN-US" style="font-size: 8pt;">  +41 840 888 888<o:p xmlns:o="urn:schemas-microsoft-com:office:office"></o:p></span></p>
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mso-ansi-language:EN-US;mso-fareast-language:#2000">F</span></b><b><span lang="EN-US" style="font-size:8.0pt;color:#538135;mso-ansi-language:EN-US;
mso-fareast-language:#2000"> 
</span></b><span lang="EN-US" style="font-size: 8pt;">+41 840 888 000</span><span lang="EN-US" style="font-size: 12pt;"><o:p xmlns:o="urn:schemas-microsoft-com:office:office"></o:p></span></p>
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mso-ansi-language:EN-US;mso-fareast-language:#2000">M</span></b><b><span lang="EN-US" style="font-size: 8pt;">
</span></b><b><span lang="EN-US" style="font-size:
8.0pt;mso-ansi-language:EN-US;mso-fareast-language:#2000"><span style="color: rgb(0, 0, 255);"><a href="mailto:sriccio@swisscenter.com" style="color: rgb(5, 99, 193);">sriccio@swisscenter.com</a></span></span></b></p>
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