Rob's reply in this thread was garbled due to <https://gitlab.com/mailman/mailman/issues/616>. The text of the reply is quoted below.
On 7/27/19 12:54 AM, Rob Lister wrote:
One thing that does occur to me is that my exim header fudge will probably cause the Message-ID header to move around from its original position, and if someone is doing hashing or actually validating (gpg signing?) the headers haven't been tampered with, then it might complain, since although the message-id hasn't changed, it might be in a different place in the headers.
Then again, mailman can make plenty of other modifications and additions to the headers anyway, so I'm not sure it matters.
Probably the more correct way to do it is only add a new header if it's missing, and if it's there, leave it alone.
This is probably possible in exim with some more variables and a lot of nested curly braces...
-- Mark Sapiro <mark@msapiro.net> The highway is for gamblers, San Francisco Bay Area, California better use your sense - B. Dylan