>
> > No  - that check is on the Recipient, not the sender.
>
> Think again. That check is on the sender.

I think we keep talking two different things.

We are talking about incoming (non-relayed email).  This has NOTHING to do
with relay settings.

If you do NOT set up the NOBODY alias, IMAIL checks the RECIPIENT to make
sure they are valid (otherwise, the mail is rejected at the envelope stage).
The sender is not checked in any way (unless anti-spam in enabled, which is
an entirely different story).

What KAMI (and many others) would like is:  At the envelope stage, if the
sender claims to be a local user and the user is not valid, reject the
email. Note, the relay settings differ in that only if the sender claims to
be local and is sending NON-LOCAL mail, would relay occur if you chose the
(very bad) setting of relay for local users.  This request simply asks for
an extension of the capabilities IMAIL already has: check incoming mail for
local (valid) user as recipient, check sender as local domain: if invalid
user, refuse mail.  This presumes that if the user claims to be a valid
local user, SMTP AUTH is invoked to receive the email (otherwise, the
spammer can simply switch to using the recipient's email addr as the
return/from addr).

However, the end effect would be to simply eliminate one of many ways
spammers get mail into your system. But, it is an effect way, as many
whitelist any sender from their own domain, even using external IP's, due to
FP's.  For example, since many are running a specific 3rd party app and have
not upgraded IMAIL to the level where they can tell if the user is SMTP AUTH
when doing spam checks, some subtract weight for a sender in the local
domain, to offset weight added by other tests.  Of course, for those not
using a 3rd party app, making this change (outlined above) would stop some
of your incoming spam (for a while).

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