[OT] How to avoid Backscatter in Sendmail

Kevin Miller Kevin_Miller at ci.juneau.ak.us
Wed Apr 21 18:25:42 IST 2010

Marcello Anderlini wrote:
> This is a production server with a lot of virtual users and virtual
> domains, I'm afraid that If I disabling relay_based_on_MX the system
> could be stop to process all email. Could I just disable
> relay_based_on_MX or I have to had some other feature to allow relay
> for virtual domains and users ?   

You don't have to disable relay - just specify the domains/ip ranges that are allowed to relay. Some examples from my access file:

#cyberspammer.com       ERROR:"550 We don't accept mail from spammers"
#sendmail.org           OK
#192.168                RELAY

You may also want to add appropriate entries in your mailertable and relay-domains files listing the domains for which you relay mail, i.e., internal systems not visible to the outside which your gateway will relay to.  (Assuming that matches your setup.)  Don't forget to hash mailertable if used...

Kevin Miller                Registered Linux User No: 307357
CBJ MIS Dept.               Network Systems Admin., Mail Admin.
155 South Seward Street     ph: (907) 586-0242
Juneau, Alaska 99801        fax: (907 586-4500

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