In the real world signature reliability matters. If a domain signs mail
as a rule then an absent or broken signature will be treated as
suspicious.
I hope you're wrong, since that violates an explicit SHOULD in RFC 4871,
and in my experience, most broken signatures are due to innocent
modification in transit, not malice.
Do you have numbers to show that broken signatures indicate that messages
are malicious, or spam, or otherwise worse than otherwise?
For that matter, since we're not talking about ADSP, what do you mean by
an absent signature? Do you track which domains sign what mail? How do
you tell what signature you're expecting? From line domain? Sender?
Message ID? Something in the Received lines?
Regards,
John Levine, johnl(_at_)iecc(_dot_)com, Primary Perpetrator of "The Internet
for Dummies",
Please consider the environment before reading this e-mail. http://jl.ly
_______________________________________________
NOTE WELL: This list operates according to
http://mipassoc.org/dkim/ietf-list-rules.html