Murray S. Kucherawy wrote: > Can anyone remember why there's a SHOULD for the downgrade to 7-bit > in RFC4871 Section 5.3, rather than a MUST? The likelihood of > breakage is so high when sending 8-bit data that DKIM almost > becomes pointless without the upgrade. > > Not advocating for this to be changed in -bis (yet), but someone's > asking me for the history behind that decision.
The top two: 1) DKIM signed mail is not an email requirement. A MUST would be too extreme. 2) There is a natural expectation for passthru non-tampering. Practical: 3) If high cost changes are required to satisfy this downgrade, it is cheaper not to sign mail at all. 4) The MSA who is DKIM-AWARE might do the translation in preparation for the DKIM signing component, but this again one of those "narrow" things that you expect adaptation or a fix to occur. The two top sentences are prevailing: 1st paragraph, last sentence: Such conversion is outside the scope of DKIM; the actual message SHOULD be converted to 7-bit MIME by an MUA or MSA prior to presentation to the DKIM last paragraph: More generally, the signer MUST sign the message as it is expected to be received by the verifier rather than in some local or internal form. That first paragraph is closer to a GateWay issue which is out of scope in DKIM. You're touching base with boundary layer INPUT requirements argument Murry, I suggest to avoid this. You can't enforce this with a MUST and if you do, you will find systems taking the easy, no cost path of not signing mail -- Hector Santos, CTO http://www.santronics.com http://santronics.blogspot.com _______________________________________________ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html