This one time, at band camp, JJ van Gorkum said:
> John Kelly wrote:
> > Every day, I get mail delivery attempts to non-existent users like:
> >
> > k2159jcd003343@isp2dial.com
> > k1mmcsoa007563@isp2dial.com
> > k1nardpb001747@isp2dial.com
> >
> >
> > These totally bogus user names are not a good dictionary attack. I
> > don't know what the spammer is trying to accomplish, since delivery is
> > impossible. The user portion almost looks like a mail queue message
> > id.
> >
> > Anyone else seeing this?
> >
> Yep, Most effective is (if you are using exim4) check if the sender has
> an MX record (from http://www.sput.nl/spam/ )
>
>
> # There has to be an MX, except in case of DSN deny message = No MX for
> envelope sender domain $sender_address_domain. See http://www.sput.nl/spam/
> hosts = ! : !+relay_from_hosts
> senders = ! :
> condition = ${if eq\
> {${lookup dnsdb{mx=$sender_address_domain}{$value}fail}}\
> {fail}\
> {yes}{no}}
Er, just:
verify = sender
will make sure the mail is routable, by either MX or A records.
Similarly,
verify = recipient
will keep you from having to deal with mail to nonexistant users.
Accepting mail for random local parts and bouncing later is bad, mmk?
--
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| ,''`. Stephen Gran |
| : :' : sgran@debian.org |
| `. `' Debian user, admin, and developer |
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