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postfix-users: RE: Fighting Backscatter

RE: Fighting Backscatter

From: Steve Jenkins <steve_at_nospam>
Date: Wed Oct 20 2010 - 03:41:37 GMT
To: "'Jeroen Geilman'" <jeroen@adaptr.nl>, <postfix-users@postfix.org>

Jeroen said:

My personal server uses:

smtpd_recipient_restrictions = permit_mynetworks,
 
permit_sasl_authenticated,
 
reject_unauth_destination,
 
reject_unknown_reverse_client_hostname,
                                                        warn_if_reject
reject_non_fqdn_helo_hostname,
                                                        warn_if_reject
reject_invalid_helo_hostname,
                                                        warn_if_reject
reject_unknown_helo_hostname,
 
reject_unauth_pipelining,
 
reject_non_fqdn_sender,
 
reject_unknown_sender_domain,
 
reject_non_fqdn_recipient,
 
reject_unknown_recipient_domain,
                                                        check_helo_access
hash:/etc/postfix/helo_access,
                                                        permit

Out of curiosity, does anyone see any drawbacks (such as possibly rejecting
valid mail) to adding "reject_invalid_hostname" to those
smtpd_recipient_restrictions? Also, some other reading I've been doing
suggest adding "smtpd_helo_required = yes" to the main.cf file. Is that
helpful/necessary, or would I already be covered there with the
"reject_invalid_helo_hostname" in the above recipient restrictions?

 

I've also read another suggestion to add "smtpd_sender_restrictions =
reject_unknown_address" to reject mail that doesn't have any return address.
I've moved all my checks to the recipient restrictions, so if I added this,
it would be my only sender restriction. Am I wrong in thinking this check is
superfluous because of the "reject_non_fqdn_sender" already in the above
recipient restrictions?

 

It's slowly starting to make more sense. Thanks again to those who have
given me helpful nudges.

 

Thanks,

 

Steve