Hi!
The lookuphost router 'qualify_single' option defaults to true. I want to
suggest to change it to default to false. If 'qualify_single' is true,
changes of the resolver configuration can have unwanted and unexpected
results.
Exim's lookuphost router tries to route all mail to a host name resulting in
appending the value of the 'domain' setting in /etc/resolv.conf to the
domain part of the mail's original destination address. If there is a
wildcard MX record for the value of the 'domain' setting in
/etc/resolv.conf, =all= mail routed by the lookuphost router will get
delivered to the host named in the wildcard MX record.
Also, the name of the 'qualify_single' setting might be misleading since all
addresses are qualified (at first try), no only those without a dot.
After all this problem might also be related to our resolver which is rather
old (SunOS 4.1.3 original), I'm not sure about this point.
Example:
On mail.foo.bar, there is a line in /etc/resolv.conf:
domain foo.bar
There exists a wildcard MX record for this:
[DNS Zone foo.bar]
* IN MX 0 mail.foo.bar.
mail IN A 1.2.3.4
mail.foo.bar knows about delivering mail to *.foo.bar in any way, for
example by a domainlist router
If 'qualify_single' is not set to false, =all= mail meant to go to the outer
world will go to the host itself:
Mail to 'user@???' is resolved as 'user@???' for which there
is an MX record to mail.foo.bar. mail.foo.bar recognizes that's herself and
delivers to the appropriate entry in the domainlist router for foo.bar.
Greetings
Moritz
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