[lug] OT: Dealing with Unreliable Mail/DNS Servers

[George Sexton]

The problem appears to be that I was getting an authoritative NXDOMAIN
response. I think I found the workaround.

The problem was sendmail first makes a AAAA DNS request. Certain broken
DNS servers incorrectly return a SERVFAIL or NXDOMAIN response rather
than the correct response of "No Records". For sendmail, the workaround
appears to be to add a magic 

define(`confBIND_OPTS',`WorkAroundBrokenAAAA') 

entry into the .mc file and re-generate the .cf file using M4.

George Sexton
MH Software, Inc.
Home of Connect Daily Web Calendar Software
http://www.mhsoftware.com/connectdaily.htm
Voice: 303 438 9585

-----Original Message-----
From: lug-bounces at lug.boulder.co.us
[mailto:lug-bounces at lug.boulder.co.us] On Behalf Of Jeffrey Siegal
Sent: Tuesday, January 06, 2004 8:58 AM
To: Boulder (Colorado) Linux Users Group -- General Mailing List
Subject: Re: [lug] OT: Dealing with Unreliable Mail/DNS Servers


You ought to be able to set things up so that a domain that simply 
fails to resolve at all, as opposed to a domain for which you get an 
authoritative "no such domain" answer, is not bounced but refused with 
a retryable failure code (4xx).  This will cause the sender to try 
again later, at which time you'll hopefully be able to resolve the 
domain.

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