Today I wrote:-
You could have blocked this by checking for bogus mx records.
In postfix (main.cf) I use the command:-
[...]
Whilst all that may be true, that isn't the reason I block from them
See transcript:-
[root(_at_)mail1 root]# telnet 203.202.24.60 25
Trying 203.202.24.60...
Connected to 203.202.24.60.
Escape character is '^]'.
220 vweb.nass.com.au ESMTP Postfix
mail from:abuse(_at_)cedex(_dot_)net
250 Ok
rcpt to:dave(_at_)henry(_dot_)st
550 Service unavailable; Sender address [abuse(_at_)cedex(_dot_)net] blocked
using
dsn.rfc-ignorant.org; Not supporting null originator (DSN)
quit
221 Bye
Connection closed by foreign host.
[root(_at_)mail1 root]#