[exim] Re: bounce messages and their potential misuse

On 2006-03-30, Peter Bowyer <peter@???> wrote:

> You're right, it wouldn't use callouts. But instead, it has a closed
> community of known senders for whom it relays, and it can safely
> assume that none of them is forging its sender address - so if it gets
> a rejection on a relayed message, it can return it to the sender
> knowing that the sender address is genuine.

I think you're saying that MTA(n-1) should be confident that it is
handling mail with good senders' addresses, although it can't know
about the recipients' addresses, whereas MTA(n) can distinguish good
and bad recipients' addresses and has to assume that MTA(n-1) has
checked the senders' addresses.

Now when we say "senders' addresses", which headers are we talking
about? For example, I send mails from my home computer with various
from-addresses (mainly one for work and one for personal stuff), none
of which is associated with my ISP.