On 02.10.2018 12:48, Johannes Bauer wrote:
> Once authenticated with m...@foo.com, the envelope sender ("MAIL
> FROM") is restricted to only the permissible variants. [...]
>
> How can I ensure in the future that the same checks are applied to the
> Header "From" field that are also applied to the evelope "From" field?
Educating the customers would be my first step. Then, you could use
milter-regex (http://www.benzedrine.ch/milter-regex.html) or similar in
your authenticated submission process:
# /etc/submission-milter-regex.conf
reject "No impersonations please"
envfrom /@gmail.com>/i
reject "Missing 'From' header or domain mismatch"
not ( envfrom /@foo.com>/i and header /^From$/i /@foo.com/i )
I cannot test this right now, but it should work. Note that users can
evade check #2 by using headers like
From: "t...@foo.com" <j...@bar.com>
but that would be malice, and reason to kick your customer's backside.
-Ralph
