The Natural Philosopher  writes:
> On 20/03/2020 16:01, Richard Kettlewell wrote:
>> The Natural Philosopher  writes:
>>> On 20/03/2020 12:26, Richard Kettlewell wrote:
>>>> The Natural Philosopher  writes:
>>>>> On 20/03/2020 10:19, Richard Kettlewell wrote:
>>>>>> Martin Gregorie  writes:
>>>>>>> Its well-known that the From: header is not used at all to
>>>>>>> transfer mail from sender to receiver - returned bounces are
>>>>>>> sent to the Reply-To address.
>>>>>>
>>>>>> No, they aren’t. Bounces are sent to the transport-level sender
address
>>>>>> (often called the “return path”).
>>>>>>
>>>>> 'envelope from'
>>>>
>>>> Yes, that too. Delivery agents often add it as a Return-Path: header as
>>>> their last act.
>>>
>>> No, they do not. Ever.
>>
>> $ grep -c ^Return-path  ~/mail/saved/2019
>> 1159
>>
> Oh dear. I wonder who added that?

Exim. It’s following the spec:
https://tools.ietf.org/html/rfc5321#section-4.4

--
https://www.greenend.org.uk/rjk/

--- SoupGate-Win32 v1.05