On 4/11/2025 12:58 PM, Richard Clayton wrote:
Email service providers will often add two, one on behalf of
the actual originator the other for themselves. A relay that
rewrites email from one domain to another will add two headers to
record the rewriting.
That's not a relay.
Relays don't change the message. And they typically only add a Received:
header
field.
they generally change the destination mailbox as well ...
MTAs don't. Ever. MDAs might.
The basics are simple: A message is sent to the specified address. It
gets to that address. What happens to it then is part of a delivery
(and re-posting) process, not message relaying.
The `delivery` process results in a new posting, to a new address,
albeit without changing the message.
The confusion about this is common, because at base it is based on
common software implementation, rather than the abstract email architecture.
If a message gets to its specified address, the handling of the message,
at that point, is not being done as part of MTA functionality.
d/
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net
bluesky: @dcrocker.bsky.social
mast: @[email protected]
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