J. Ryan Earl wrote:

> Hello,
> 
> I'm having a problem with an Exim MTA that I manage.  I noticed late 
> last week load on the server was increasing in quantized intervals, ie 
> load was going up by exactly 1 in puntuated periods.  After 
> investigating more, it turns out some emails were looping between exim 
> processes because of a bad IPv6 AAAA record, but first I would like to 
> give a bit of background and information on the server host in question 
> before I ask for possible permanent workarounds:
> 
> Exim is running on a RHEL4 with the default Redhat Exim RPM--I'm trying 
> to not build my own version of exim:
> # rpm -q exim
> exim-4.43-1.RHEL4.5

*snip*


> Here we see the problem, the AAAA record for clsmail.com is setup 
> incorrectly.  The temporary workaround is to stop exim for a minute to 
> let the email timeout in looping to itself, however, as soon as an 
> autosearch for this user is run again the email loop starts up.  Now I'm 
> trying to figure out the best permanent workaround.  I did some research 
> and basic googling on the matter and found: 
> http://www.exim.org/exim-html-4.62/doc/html/spec_html/ch13.html#id2569429
> 
> disable_ipv6 appears to have been added after Exim version 4.43, so I 
> can't use that.
 >  Instead I added the following to exim.conf:
> 
> # turn off IPv6 lookups
> dns_ipv4_lookup = true
> 
> However, that didn't seem to help any, the email loop resurfaces.  I'm 
> hoping that I won't have to build my own custom installation of Exim to 
> fix this problem as this is installed on a heavily used production 
> system and a new Exim installation would be a huge variable I'd like to 
> avoid.  Does anyone know of a permanent workaround to disable IPv6 AAAA 
> lookups with the stock RHEL4 version of Exim?
> 
> Thanks in advance,
> 
> J. Ryan Earl
> Systems/Network Engineer
> dynaConnections Corp
> 512.306.9898
> 

Sanity check. Or 'Why are you HERE'.

Exim has long-since provided the tools that you need to work around someone 
elses error, but you would rather not *use* those tools by upgrading to a more 
current Exim release.

You apparently haven't explored another obvious route - that of asking the 
entity with the defective IPV6 DNS entry to help themselves - and the world 
at-large - by fixing it.

Then why not just ask the sole correspondent with a problem for an alternate 
e-mail address that works as-is so you may continue running your obsolete 
installation?

Exim upgrades - save from 3.X to 4.X - are nothing like a 'huge variable'.
au contraire - they are about as transparent and backward-compatible as exists.

Bill




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