require_rdns.m4 (Was Require RDNS?)

Steve Freegard steve.freegard at
Thu Aug 17 20:46:33 IST 2006

Hi Jeff,

Jeff A. Earickson wrote:
> Gang,
> I rolled out require_rdns.m4 this morning and my phone is starting
> to ring.  I have discovered that our network guy created (at least)
> two entire subnets in DHCP but never bothered to create DNS zones
> for them, so I have whole chunks of my campus not able to send email!
> My question for you sendmail mc gurus:  instead of doing
> $#error $@ 5.7.1 $: 550 RDNS: Fix reverse DNS for $1
> in require_rdns.m4, I want to just log the message and go on (dry-run
> mode), something like:
> $#print $@ 5.7.1 $: 550 RDNS: Fix reverse DNS for $1
> Anybody know how to tweak an mc to just syslog an action?

I'm not sure how to do that -- but you could 'whitelist' your internal 
IP address ranges using the access.db if you have the latest version of 
the hack (see: - 

rdns:192.168.47		OK

Just a thought.


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