Quoting Michael (mb_devuan-mailinglist@???):

> I am going to say, that the Trinity Desktop Environment (TDE) Users
> mailing list seems to send from/to ProtonMail without the reply to
> issue the Devuan Users list has. The list admin, and owner of the
> project, is Timothy Pearson, and his publicly published email is:

If you're saying that the TDE Users mailing list doesn't apply the
Mailman-recommended DMARC mitigation, then you are correct that no
MLM-level munging of the sender's 'From: ' header (or appending of a
Reply-To: header for DMARC-mitigation reasons) will be applied to any
subscriber's mail.

Unfortunately, that would _also_ mean that TDE Users postings from domains
with aggressive DMARC policies will encounter deliverability issues to
receiving domains that enforce DMARC (e.g., to GMail). And this bad
situation will persist for TDE Users members unles/until the listadmin
applies DMARC mitigations.

> The headers are fairly different, not that I know what specifically ‘fixes’
> this issue, but I’ll guess it would hopefully give a clue as to what/where
> the fix lies.

{sigh} Nobody listens.

There is nothing needing a 'fix' (unless you wish to argue with
operators of domains publishing aggressive DMARC policies (p=reject or
p=quarantine) and convince them that such is an unwise policy). In a
world where DMARC is being rolled out by many domains, mailing lists can
either attempt to mitigate the DMARC-caused damage, or do nothing and
let some subscribers and their readers figure out the hard way why
certain posters aren't being received at certain domains (e.g., GMail)
and are getting gradually auto-unsubscribed by Mailman on account of
excessive 'bounce scores'.

-- 
Cheers,                                            "He who laughs last, lasts."
Rick Moen                                                       -- Leo Rosten
rick@???
McQ! (4x80)