Invalid DKIM signatures in this list

[John Levine]

In article <20181126125259.GB86999 at admin.sibptus.ru> you write:
>Dear Colleagues,
>
>I have noticed that the Mailman which manages this list keeps the 
>sender's "DKIM-Signature:" header intact but modifies the body of the 
>message by adding a footer.
>
>This behavior invalidates the sender's digital signature with
>"dkim=fail (body hash mismatch; body probably modified in transit)". 

Quite right.  That's how DKIM works.

>Whom do I contact about it?

Nobody.  See RFC 6376, section 6.3.

R's,
John