The mailing list for listmasters using Sympa

[David Carter <address@concealed>]

On 2021-01-11 08:00, IKEDA Soji wrote:

> It is a discussion that has repeated many times in anywhere dealing
> with mailing list system.  However, removing “Sender:” field with
> list’s address, instead of originator’s address, will prevent
> delivering any messages sanely via mailing lists among the Internet.

The envelope sender / Return-Path: / SMTP MAIL FROM obviously has to be 
address@concealed to collect bounces.

I'm curious why the Sender: header in the message body also needs to be 
set. Two potential reasons come to mind:

1) Broken MTAs which replace the envelope sender with the body Sender:
2) Protection again mail loops.

I'm willing to believe that I'm missing something really obvious here, 
having never tried to remove the Sender: header myself.

When my users ask, I just tell them that Microsoft are "special". 
Unfortunately it is becoming more obvious these days as we migrate to 
Microsoft 365.