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Spam fighting ¶

Very good spam fighting techniques can be found on ACME website.

My setup and techniques are following:

• Nolisting:

  stargrave.org mail is handled by 10 mailfake0.stargrave.org.
  stargrave.org mail is handled by 20 mail2.stargrave.org.
  stargrave.org mail is handled by 30 mailfake1.stargrave.org.
  

  mailfake domains exist, have an address, but no daemon listens on them. Many robots will connect only to the first MX.

• I also add Null MX record for domains are not intended to accept email.
• Check for reverse DNS record works very good.
• Postfix configuration options that work relatively good:

  disable_vrfy_command = yes
  strict_rfc821_envelopes = yes
  smtpd_helo_required = yes
  smtpd_recipient_restrictions =
      permit_mynetworks,
      reject_unauth_pipelining,       # Do not allow PIPELINE at all
      reject_non_fqdn_helo_hostname,  # Reject HELO with non FQDN
      reject_invalid_helo_hostname,   # Reject malformed HELO
      reject_unauth_destination,      # Reject unknown destination
      reject_unknown_client_hostname, # check IP->name mapping,
                                      # check name->address mapping,
                                      # check name->address match
      check_policy_service inet:127.0.0.1:10023
  smtpd_client_restrictions = sleep 5, reject_unauth_pipelining
  smtpd_delay_reject = no
  
  # Some mail is rejected at all from some domains
  smtpd_sender_restrictions = hash:/usr/local/etc/postfix/access
  

• Greylisting weapon. This works very well, however will increase legitimate mail delivery time for the first time.
• I refuse to use any blacklists (RBL, DNSBL), because in that case delivery of email is under control of someone else. I do not trust them. Moreover there is high risk of false positives. I do not like when people use this technology, marketing bullshit, unfair play.
• Own manual maildrop rules that places mail directly into /dev/null, or spam folder. I check spam folder once or twice a week and quickly wipe it if visually it have obvious spam.
• I used Bogofilter Bayesian filter, but currently it is an overhead.