[Esd-l] spam / From address verifier

[Peter Warasin]

hi

On Thu, 18 Jul 2002, John D. Hardin wrote:
> > if someone want to use it.. i put it on my server
> > www.darkrealms.org/checkfrom.drg
> This would be possibly be useful for dynamically determining
> NOTIFY_SENDER.
yes thats a good idea.. 
but i think that my script has a bug somewhere.. im not sure.. but it
looks like
i think i have to read a couple of rfcs cause some mailservers does reject
mails of emailadresses which *are* real accounts.. so if you want to use
that code.. wait until i found the bug ,)

> Bear in mind the overhead of a response mail attempt on every inbound
> message. You probably only want to do this if the message fails a
> whitelist check.
hm.. yes.. the mailserver is also a target for dos-attacks if the script
is runnig. if someone is sending mails with an emailadress of an
inexistent domain and the mailserver let it pass, or if the lookup for
mx-hosts results an inexistent host, the script must wait for the
dns-timeout. 
i think thats the greater problem but i have no chance to solve this. :(

i planned to add a caching feature which stores well-known
(and well-known inexistent) emailadresses in a hash-db's but i had no time
to do this
i think it is the only possibility to reduce traffic and the dos-problem

peter