2 messages in net.sourceforge.lists.courier-users[courier-users] 417 DNS lookup failure
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Morgan MassenaAug 2, 2002 5:57 pm 
Sam VarshavchikAug 2, 2002 6:15 pm 
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Subject:[courier-users] 417 DNS lookup failureActions...
From:Morgan Massena (mmas@ipowerplant.com)
Date:Aug 2, 2002 5:57:40 pm
List:net.sourceforge.lists.courier-users

I just happened to look at a tail -f of my maillog a little bit ago and noticed this showing up 3-5 times per second!

---- Aug 2 17:15:08 bsd1 courieresmtpd: started,ip=[4.37.106.187] Aug 2 17:15:09 bsd1 courieresmtpd: error,relay=4.37.106.187,from=<2228@manager.sendoutmail.com>: 417 DNS lookup failure: manager.sendoutmail.com. Try again later.

---- I did a `grep -c sendoutmail.com /var/log/maillog` to get the response of 20827! Nearly 21,000 times today!

I had temporarily blocked that class C from my firewall--which got flushed when I reloaded it from the conf file.

Is it possible to either blackhole or send a 5yz reply when a host is flooding the server with the exact same request? In my opinion firewalling each host seems like an inefficient hack.

Thanks for your input!

Morgan Massena Programmer/Systems Administrator IPowerPlant

---------------- 13 S. Washington Spokane, WA 99201

---------------- Office: 509.252.3939 Cell: 509.263.7493 Email: mmas@ipowerplant.com