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.
I think Pete's analysis is correct, but my advice would be to take
it out altogether. We don't have any great insight into the warts
of what paths are likely to downcode a message and what paths aren't,
so I would prefer not to purport to offer advice about it.
R's,
John
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