On 24Nov2020 12:09, Ian Zimmerman <[email protected]> wrote: >On 2020-11-24 17:22, Chris Green wrote: >> > > I'm on a couple of mailing lists that have recently moved from >> > > Yahoo Groups to groups.io. For DMARC (so they claim) groups.io >> > > change the senders E-mail address as follows:- >> > > >> > > Sender Name <[email protected]> >> > > >> > > becomes:- >> > > >> > > "Sender Name via groups.io" <[email protected]> > >> It only happens to users from some domains. [...] > >It is because those senders subscribed with an address covered by a >strict DMARC policy. If their address is not munged by the list, their >messages will be bounced back to the list by almost everyone if they >fail a DKIM check (and that's almost always). [...] > >There's no good automatic solution to build into a MUA for this, as far >as I know. The best you can do is write a macro to extract the true >sender, and feel lucky for using a MUA that allows that :-)
I have an unmangle step in my mail filer. I'll list the rules at the bottom of this message. Basicly, for particular sources I hack the From: line around. For yahoo lists the original address was embedded in the From: header itself, for [email protected] the Reply-To: header holds the original author, for [email protected] the X-Old-From: header holds it, for [email protected] it is in the X-MailFrom: and so forth. So there's a suite of special purpose rules below. The rule syntax below is "target condition...", so each of the: from:s/this/that/ lines is a "target" and the other lines constraint which messages it is applied to. I imagine you could do something with procmail like this. See the "formail" command. If formail won't do it, a sed script probably will. Note that this of course mangles the headers, a price I've been willing to pay for sanity. Cheers, Cameron Simpson <[email protected]> # undo Yahoo Groups DKIM/DMARC mangling # if we ever check the validity of this stuff it will need to be before this step from:s/"(?P<fullname>.*\S)\s+(?P<coreaddr>\S+@\S+)\s+\[(?P<listname>[^ ]*)\]".*<(?P=listname)(-noreply)[email protected]>/"$fullname" <$coreaddr>/ sender:/@yahoogroups.com from:/@yahoogroups.com> from:s/"(?P<fullname>.*\S)\s+(?P<coreaddr>\S+@\S+)\s+\[(?P<listname>[^ ]*)\]".*<(?P=listname)@yahoogroups.com>/"$fullname" <$coreaddr>/ sender:/@yahoogroups.com from:/@yahoogroups.com> from:s/"(?P<coreaddr>\S+@\S+)\s+\[(?P<listname>[^ ]*)\]".*<(?P=listname)@yahoogroups.com>/<$coreaddr>/ sender:/@yahoogroups.com from:/@yahoogroups.com> from:s/.*/$reply_to/ sender:[email protected] from:/ via Mercurial <[email protected]> # undo Linux Australia header mangling from:s/.*/$reply_to/ sender:[email protected] from:[email protected] from:s/.*/$x_mailfrom/ from:[email protected] x-mailfrom:/@ list-id:/core-mentorship.python.org/ from:s/.*/$reply_to/ from:([email protected]|[email protected]|[email protected]|[email protected]) # fedoraproject.org x-mailfrom from:s/ via users <[email protected]>/ <$x_mailfrom>/ from:([email protected]) # googlegroups x-original-from from:s/ via users <[email protected]>/ <$x_original_from>/ from:[email protected]
