View source for Prevent Spam from valid sender/recipient

[[User_Tips_%26_Tricks#Anti_Spam|Back]]<br>
'''How to prevent spam from a spoofed local account.'''

Example SMTP Log:

 08-27 05:54:35 CHKUSER accepted sender: from <valid.email@account.no::> remote <[113.22.203.172]:unknown:113.22.203.172> rcpt <> : sender accepted
 08-27 05:54:35 CHKUSER accepted rcpt: from <valid.email@account.no::> remote <[113.22.203.172]:unknown:113.22.203.172> rcpt <valid.email@account.no> : found existing recipient
 08-27 05:54:35 policy_check: local valid.email@account.no -> local valid.email@account.no (UNAUTHENTICATED SENDER)
 08-27 05:54:35 policy_check: policy allows transmission
 08-27 05:54:35 spamdyke[28493]: ALLOWED from: valid.email@account.no to: valid.email@account.no origin_ip: 113.22.203.172 origin_rdns: (unknown) auth: (unknown) encryption: (none)
 08-27 05:54:39 simscan:[28494]:CLEAN (7.90/12.00):3.1911s:***SPAM*** Hi recipient, be our guest. 70% off for you.. on is the:113.22.203.172:valid.email@account.no:valid.email@account.no 

* Use spamdyke, and blacklist your local domain(s). This is counter intuitive, but works great. In the <pre>/etc/spamdyke/blacklist_senders</pre> file, add: <pre>@mydomain.com</pre>

* All of your domains' submissions must be authenticated for this to work. If you have some web apps (for instance) that submit w/out authenticating (you have them approved for relay in tcp.smtp) then you can't use this method. My suggestion in this case is to modify the web app to authenticate.

* Webmail should be configured to authenticate, in which case you don't need the 127.: line in tcp.smtp. This is a trivial change in <pre>/etc/squirrelmail/local_config.php:
:$smtpServerAddress  = 'localhost';
:$smtpPort           = 587;
:$smtp_auth_mech     = 'login';</pre>

(reference [http://www.mail-archive.com/qmailtoaster-list@qmailtoaster.com/msg29093.html email list archive])