On 2009-10-06 at 09:58 -0400, Grant Peel wrote:
> Hi all,
>
> I would like to set the outgoing interface to the IP address assigned to the user's domian.
>
> The problem I am encountering is that not all domains have thier MX set to an IP on our server (because some domains are using a mail filtering server that relays the message to our server after filtering).
>
> Is there a way to rewrite the transport's 'interface' lines below, so it will attempt to use the MX, then the A record, then a default IP (the servers main IP) in that order?
I believe so.
Note that a dnsdb mxh lookup will return multiple hosts and you're not
setting a list separator, so that would also fail if sending with a
sender address in a domain with multiple MX records.
Also, the interface is supposed to be specified as a list of IP
addresses.
How about IPv6? Heck, it's easier to have IP-per-customer with IPv6.
[Beware: long lines below, 80-column viewers may wrap or need scroll]
IPv4-only:
${lookup dnsdb{>; a= <; ${lookup dnsdb{>; mxh=$sender_address_domain}} ; $sender_address_domain }}
This says to do a lookup, using semi-colon as list separator for output,
of the A records given as a semi-colon separated list; we then use MXH
pseudo-type items to get the MX hostnames, results separated by
semi-colon, and then add the domain itself on at the end, all used as
input.
IPv6/IPv4:
${lookup dnsdb{>; aaaa= <; ${lookup dnsdb{>; mxh=$sender_address_domain}} ; $sender_address_domain }} ; \
${lookup dnsdb{>; a= <; ${lookup dnsdb{>; mxh=$sender_address_domain}} ; $sender_address_domain }}
Note the marked similarity there.
Now, I forget whether or not the interface directive ignores IPs not
locally bound or whether or not that results in an error. Skimming the
source, it looks like you need to filter this. The @[] list includes
all the IP addresses of the host that Exim is running on. We can use
that to filter.
${filter{<string>}{<condition>}}
Conveniently, filter reuses the list separator for the input list when
generating the output list.
So:
${filter{<; ${lookup dnsdb{>; aaaa= <; ${lookup dnsdb{>; mxh=$sender_address_domain}} ; $sender_address_domain }} ; \
${lookup dnsdb{>; a= <; ${lookup dnsdb{>; mxh=$sender_address_domain}} ; $sender_address_domain }}}\
{match_ip{$item}{@[]}}}
Finally, remember to tell interface of the list separator and the
default IPs:
interface = <; $STUFF_FROM_ABOVE ; @[]
> # interface = ${lookup dnsdb{a=${lookup dnsdb{mxh=$sender_address_domain}}}}
Lather, rinse, repeat.
Around about now, I wish Exim had user-defined functions written in
Exim's configuration language. ;) Well, you can always write it in
Perl or C and use the ${perl...} or ${dlfunc...} expansions.
-Phil
