MTA Removes CRLF From Header Before Passing To Milter
Last updated on SEPTEMBER 01, 2017
Applies to:Oracle Communications Messaging Server - Version 7.0.0 and later
Information in this document applies to any platform.
Using: Oracle Communications Messaging Server 7u4 p27
The original milter specification had this to say about sending header information to the milter server:
Note that this is *not* "passing the header unchanged"- if if were there would be CRLFs in there.
This should not be a useful thing since the specifications are also clear that header folding is free of semantics. However, DKIM made an exceptionally poor design choice in providing the "simple" header canonicalization where the folding points do matter, and unfortunately some systems, apparently including PayPal, make use of this canonicalization.
An option to map CRLF line breaks to LFs rather than discarding them is therefore needed in the milter interface.
Requesting an Enhancement Request to have the MTA’s behavior of removing all CRLFs from the header be configurable so that we can tell it to not do that as it’s breaking DKIM signatures from PayPal and others.
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