On 2/7/26 12:28, Jim Lawson wrote:
LISTSERV is not as tweak-able as you would think in this regard. It has
some code which seems to look into the DMARC policy for each sender, and
if your sending domain specifies p=reject or p=quarantine in its DMARC
policy, then it will automatically re-write your sender address when
distributing a list message so it does not collide with the DMARC policy.
Ah. That explains the why some but not all email addresses are rewritten.
> If you're curious, the docs are here
Unfortunately I am curious....
If the message comes from such a domain, LISTSERV rewrites the "From:" address
to the format
[token][email protected]
Fine if the rewrite actually came from the postmaster, and they
enveloped the original message so mailing list members could contact
each other privately with their own email addresses, but...
(see example below). The poster's full name is left unchanged. Most
mail clients do not show the actual address, only the name, so most
users will not see any obvious difference
That is ripe for confusion. I'm sure they made that choice so you get
some useful information in your client's message index, but still the
proper rewrite would be "John Smith via <[email protected]>"
along with an enveloped message showing John Smith's actual From address...
If a list member decides to send a private reply to the sender (i.e.
not to the list), via the re-written special address, it is routed
back to LISTSERV, which forwards it to the original "From:" address.
The token is unique to each sender and only works via the same
LISTSERV instance.
Wow. A private reverse mailing list for every member. This whole thing
is getting clever in bad way.
The original sender's email address must be in there, since that is the
"contract" for how people identify each other on the list.
There are all kinds of point of confusion:
1. With this design, there could be two or three John Smith's on the
list with different email addresses. Some for Joan Jones.
2. Now the honest sender's identities are confused publicly on the list.
Oops!
3. Now when an honest John Smith talks to an honest Joan Jones through a
private message, both the sender and the receiver could be confused.
Oops I didn't mean for you to see that private message!
4. A sinister John Smith could show up and spoof the others publicly.
5. A sinister John Smith could show up, stay hidden by never publicly
the posting to list, but spoof the others privately.
All this to say that message must stay associated with their original
sender when the email address is the unit of identity in the system.
It gets back to what I was alluding to in my message. It is a fine idea
for post offices to postmark messages with the postmaster's identity,
but it is a very bad idea for post offices to sign letters for people,
and this is essentially what is happening.
... or maybe I'm jumping to conclusions. I've only read the top of those
docs and ran out of time. Thanks for the link Jim.
If people could sign their own messages, then mailing list software
would be pretty simple, just check the return address of incoming
messages against the list, accept or reject, envelope them, and finally
broadcast them.
--
Anthony Carrico
