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mx and local host error

 

 

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d.hill at yournetplus

Nov 4, 2009, 7:31 PM

Post #1 of 3 (139 views)
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mx and local host error

I have an Exim 4.69 test server running as a gateway (filter server)
which filters and passes messages onto our internal server. I have
been periodically getting a few messages frozen with the error:

sample[at]spis.net: lowest numbered MX record points to local host

The MX records for spis.net are set up as such:

spis.net. 3600 IN MX 10 smtpgate.ndunet.com.
spis.net. 3600 IN MX 10 smtpgate.yournetplus.com.
spis.net. 3600 IN MX 20 smtpgate.ndunet.com.

smtpgate.yournetplus.com happens to be the server these errors are
occuring on.

I believe this has something to do with how the router section is set
up but can not pinpoint what. Here is the router section:

begin routers

relay_to_domains:
driver = manualroute
transport = remote_smtp
route_data = ${lookup{$domain}lsearch{/usr/local/etc/exim/relay_to_domains}}
ignore_target_hosts = +bad_host_addresses

dnslookup:
driver = dnslookup
domains = ! +local_domains
transport = remote_smtp
ignore_target_hosts = +bad_host_addresses
no_more

system_aliases:
driver = redirect
allow_fail
allow_defer
data = ${lookup{$local_part}lsearch{/etc/aliases}}
user = mailnull
group = mail
file_transport = address_file
pipe_transport = address_pipe

userforward:
driver = redirect
check_local_user
file = $home/.forward
no_verify
no_expn
check_ancestor
file_transport = address_file
pipe_transport = address_pipe
reply_transport = address_reply
condition = ${if exists{$home/.forward} {yes} {no} }

localuser:
driver = accept
check_local_user
transport = local_delivery
cannot_route_message = Unknown user

relay_to_domains contain entries like such:

spis.net: 162.42.148.120

bad_host_addresses contain a list of IP addresses in CIDR format of
the IANA private IP space (internal or reserved).


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exim-users at spodhuis

Nov 4, 2009, 10:31 PM

Post #2 of 3 (128 views)
Permalink
Re: mx and local host error [In reply to]

On 2009-11-05 at 03:31 +0000, d.hill[at]yournetplus.com wrote:
> I have an Exim 4.69 test server running as a gateway (filter server)
> which filters and passes messages onto our internal server. I have
> been periodically getting a few messages frozen with the error:
>
> sample[at]spis.net: lowest numbered MX record points to local host
>
> The MX records for spis.net are set up as such:
>
> spis.net. 3600 IN MX 10 smtpgate.ndunet.com.
> spis.net. 3600 IN MX 10 smtpgate.yournetplus.com.
> spis.net. 3600 IN MX 20 smtpgate.ndunet.com.
>
> smtpgate.yournetplus.com happens to be the server these errors are
> occuring on.
>
> I believe this has something to do with how the router section is set
> up but can not pinpoint what. Here is the router section:
>
> begin routers
>
> relay_to_domains:
> driver = manualroute
> transport = remote_smtp
> route_data = ${lookup{$domain}lsearch{/usr/local/etc/exim/relay_to_domains}}
> ignore_target_hosts = +bad_host_addresses
>
> dnslookup:
> driver = dnslookup
> domains = ! +local_domains
> transport = remote_smtp
> ignore_target_hosts = +bad_host_addresses
> no_more

So the lowest-numbered MX complaint is coming from the dnslookup Router.
Therefore mail was not accepted by your relay_to_domains Router where
you are the primary MX.

Are there domains for which you are the MX where the domain does not
occur in relay_to_domains?

Are there domains in relay_to_domains which does route to RFC1918
address space? Your ignore_target_hosts restriction makes lots of sense
on a DNS lookup but less sense on a manualroute Router (depending on
where the input data comes from).

You provide a fabricated example bounce -- have you actually seen a
bounce for that domain, when it was present in the relay_to_domains file
with an address not in RFC1918?

What is the process by which /usr/local/etc/exim/relay_to_domains is
updated? Is there a race condition where the file is replaced by an
automatic process which unlinks one file and then links in the new
content, so that if Exim is trying to read it at that time then the file
does not exist? Do you have revision histories of the content of this
file to be sure that spis.net has not temporarily disappeared (assuming
automated processes maintain it)?

The debugging question is "When is a domain with lowest MX pointing to
me not listed in relay_to_domains with an acceptable IP?"

-Phil

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d.hill at yournetplus

Nov 5, 2009, 3:42 AM

Post #3 of 3 (127 views)
Permalink
Re: mx and local host error [In reply to]

Quoting Phil Pennock <exim-users[at]spodhuis.org>:

> What is the process by which /usr/local/etc/exim/relay_to_domains is
> updated? Is there a race condition where the file is replaced by an
> automatic process which unlinks one file and then links in the new
> content, so that if Exim is trying to read it at that time then the file
> does not exist? Do you have revision histories of the content of this
> file to be sure that spis.net has not temporarily disappeared (assuming
> automated processes maintain it)?
>
> The debugging question is "When is a domain with lowest MX pointing to
> me not listed in relay_to_domains with an acceptable IP?"

You hit the nail right on the head. I had 'freeze_tell = postmaster'
in the config so I would get report on messages that may get frozen.
Looking at those messages now, I do see it is happening when
relay_to_domains gets directly updated (every 15 minutes). I'll have
to change the method it gets created. Perhaps create a temp file and
raname it into place. Sometimes it does take 20-30 seconds to create.


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