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ominug
Asked: 2020-08-12 04:02:21 +0800 CST

Modifying date breaks DKIM signature. Alternatives?

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On our Postfix server we previously removed the Date header from incoming emails and had Postfix automatically add it again to prevent spoofing the date and to work around mail servers with off clocks. However, this breaks DKIM signatures which include the Date header. Is there a way with Postfix to keep the DKIM signature intact while recording the receive timestamp in a mail header (and optimally having it shown in MUA UIs)?

Previous and abolished solution:

/etc/postfix/main.cf:

header_checks = pcre:/etc/postfix/maps/header_checks.pcre
always_add_missing_headers = yes

/etc/postfix/maps/header_checks.pcre:

/^\s*Date:/              IGNORE
postfix dkim

1 Answers

  1. Best Answer
    1. Configure the server to append a Received header on received messages.
    2. Configure the mail client/MUA that displays the timestamps (or install an add-on like: IMAP Received Date)
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