在 exim 上面作 anti spam

在網路上看了一堆網頁，也摸索了好一陣子，剛才弄出這些設定：

• 在 HELO 或 EHLO 指令時作檢查的 acl name 是 check_hello：
  

  check_hello:

  deny message = HELO/EHLO with my ip address. You are not me.
  log_message = HELO/EHLO my.ip
  condition = ${if eq {$sender_helo_name}{###.###.###.###} {yes}{no}}

  deny message = Fine, then the mail I accept is also none
  log_message = HELO/EHLO none
  condition = ${if match {$sender_helo_name}{none} {yes}{no}}

  accept

• MAIL 用的 acl name 是 check_mail ：
  

  check_mail:

  deny message = $sender_host_address is listed in $dnslist_domain
  hosts = !+relay_hosts
  !authenticated = *
  dnslists = bl.spamcop.net : \
  sbl.spamhaus.org : \
  list.dsbl.org : \
  cbl.anti-spam.org.cn

  deny message = Fake Yahoo, so you must be spam.
  log_message = Fake Yahoo
  senders = *@yahoo.com
  condition = ${if match {$sender_host_name}{\Nyahoo.com$\N}{no}{yes}}

  deny message = Fake hotmail, so you must be spam.
  log_message = Fake hotmail
  senders = *@hotmail.com
  condition = ${if match {$sender_host_name}{\Nhotmail.com$\N}{no}{yes}}

  deny message = Fake MSN, so you must be spam.
  log_message = Fake MSN
  senders = *@msn.com
  condition = ${if match {$sender_host_name}{\N(hotmail|msn).com$\N}{no}{yes}}

  deny message = Fake AOL, so you must be spam.
  log_message = Fake AOL
  senders = *@aol.com
  condition = ${if match {$sender_host_name}{\Nmx.aol.com$\N}{no}{yes}}

  deny message = Fake Gmail, so you must be spam.
  log_message = Fake Gmail
  senders = *@gmail.com
  condition = ${if match {$sender_host_name}{\Ngoogle.com$\N}{no}{yes}}

  accept

• DATA 用的 acl name 是 check_data：
  

  check_data:

  deny message = Message SHOULD have Message-ID: but does not
  condition = ${if !def:h_Message-ID: {1}}

  deny message = Message SHOULD have Date: but does not
  condition = ${if !def:h_Date: {1}}

  accept

要讓 exim 在 HELO（或 EHLO）、MAIL 與 DATA 指令時作檢查，設定檔裡面要有這三行：

acl_smtp_mail = check_mail
acl_smtp_helo = check_hello
acl_smtp_data = check_data

目前在 log 看到的成效還不錯。

參考網址：

• Stopping Spam in the ACL
• Exim 4.20 Specification chapter 37 – Access control lists
• HOWTO – Using DNS Block Lists (DNSBLs)