ietf-dkim
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Re: [ietf-dkim] Postfix: change of Content-Transfer-Encoding breaks DKIM signature / RFC recommendation

2009-03-25 17:49:16
Florian Sager:
According to the mails below the RFC compliant change of content
encoding in MTA-forwarding may break signatures that follow the RFC 4871
recommendation to include header "Content-Transfer-Encoding" in the
signature. This header should be removed from section 5.5. Recommended
Signature Content (The following header fields SHOULD be included in the
signature ...).

Unfortunately, this does not solve the problem.  The 8bit-MIME to
7bit conversion as required(*) in RFC 1652 replaces the entire
message body, and therefore it invalidates DKIM signatures even
when the Content-Transfer-Encoding header is not signed.

Just like other MTAs that implement 8bit-MIME according to the rules,
the Postfix SMTP client has an option to ignore the rules and send
8bit-MIME anyway.

        Wietse

(*) Either convert the body, or return the message as undeliverable.
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