From: Phil Pennock Date: Wed, 23 May 2012 16:58:18 +0000 (-0400) Subject: Doc: document when dnslookup will decline X-Git-Tag: exim-4_80_RC5~4 X-Git-Url: https://vcs.fsf.org/?a=commitdiff_plain;h=18fc07b9b01f352a88407704a4e2d850151620b4;p=exim.git Doc: document when dnslookup will decline --- diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 96f35fe4b..31766a637 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -17103,6 +17103,40 @@ look for A or AAAA records, unless the domain matches &%mx_domains%&, in which case routing fails. +.new +.section "Declining addresses by dnslookup" "SECTdnslookupdecline" +.cindex "&(dnslookup)& router" "declines" +There are a few cases where a &(dnslookup)& router will decline to accept +an address; if such a router is expected to handle "all remaining non-local +DNS", then it is important to set &%no_more%&. + +Reasons for a &(dnslookup)& router to decline currently include: +.ilist +The domain does not exist in DNS +.next +The domain exists but the MX record's host part is just "."; this is a common +convention (borrowed from SRV) used to indicate that there is no such service +for this domain and to not fall back to trying A/AAAA records. +.next +Ditto, but for SRV records, when &%check_srv%& is set on this router. +.next +MX record points to a non-existent host. +.next +MX record points to an IP address and the main section option +&%allow_mx_to_ip%& is not set. +.next +MX records exist and point to valid hosts, but all hosts resolve only to +addresses blocked by the &%ignore_target_hosts%& generic option on this router. +.next +The domain is not syntactically valid (see also &%allow_utf8_domains%& and +&%dns_check_names_pattern%& for handling one variant of this) +.next +&%check_secondary_mx%& is set on this router but the local host can +not be found in the MX records (see below) +.endlist +.wen + + .section "Private options for dnslookup" "SECID118"