On Wed, 15 Nov 2006 14:39:47 +0000 "K.J. Petrie (Instabook)"
<kjpetrie(_at_)instabook(_dot_)com> wrote:
As I understand it, a REJECT happens when an MTA refuses to accept the
message. A bounce happens when the previous MTA attempts to advise the
sender
of non-delivery. Is that right?
Close. BOUNCE is when an MTA (or MUA, but this is rare) generates a
message sent to the address in the Mail From/Return Path. It can come
anywhere in the e-mail sending/delivery chain.
The key point is that bounces must only be sent to validated addresses.
The originating MTA should be able to bounce safely since they are dealing
with an authorized user that has been authenticated (there are multiple
ways to do this, e.g. SMTP Auth). Downstream, bouncing is much more
problematic and must be avoided (with the limited exception of bouncing for
non-SPF reasons to an address that passed SPF).
Scott K
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