kig@??? wrote:
> i heard there a lot of custom spam prevention methodics used in MTA
> during SMTP session time currently i'm interested in a one when mail
> is prohibited in case of "too many not found recipients in TO header."
> Is it reasonable to use it in production and does not violate
> netiquette? Or there are some more methodics (where to read?).
from rfc2821:
recipients buffer
The minimum total number of recipients that must be buffered is
100 recipients. Rejection of messages (for excessive recipients)
with fewer than 100 RCPT commands is a violation of this
specification. The general principle that relaying SMTP servers
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
MUST NOT, and delivery SMTP servers SHOULD NOT, perform validation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
tests on message headers suggests that rejecting a message based
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
on the total number of recipients shown in header fields is to be
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
discouraged.
^^^^^^^^^^^^
and by the way, I see almost no spam with over than one recipient in
'To:' header, with no more than five in any of these.
IMHO the way to go is to do HELO checks (malformed domains, IP addresses
not matching sender's one, HELO with my FQDN) and greylisting. I rarely
have any spam from zombies and ratware passing HELO and greylisting
checks.
MIME checks are nice, too.
--
Stanisław Halik,
http://tehran.lain.pl
