On 10/12/25 11:59 AM, Andrew C Aitchison via mailop wrote:
What would we need in order for SMTP TLS client certificates to have
a useful place in authenticating the sender ?
Please clarify who / what "the sender" is.
1) The person that strung together the words in the body of the email?
(author?)
2) The person that put those words into email form and submitted to an
MTA? (sender in RFC 822 header sense?)
3) The system connected to the receiving MTA? (other side of the SMTP
connection)
I'm not trying to be pedantic here, but I think it makes a difference.
My personal use case is #3, authenticating the remote connected MTA (or
MSA) that's sending the message to my receiving MTA.
Specifically I already have to have, and have to protect, a public
certificate and private key for my hosts that I must keep secure. So
re-using those credentials for multiple things as opposed to needing to
secure additional credentials has some value to me.
This is especially true when the IP address may change and can't be used
as a form of authentication.
I don't think that a hop-by-hop security mechanism in and of itself can
vouch for #1 nor #2. At least not without a LOT more complications
somewhat akin to some of the complications with RPKI for BGP trying to
vouch for the path.
--
Grant. . . .
unix || die
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