The
process that sendmail uses to resolve a name is described in ?§9.2 on page 325.
When sendmail finds that a hostname is really an MX record, it attempts to look up the
address (which can be an A or AAAA record) for the host that handles mail receipt. That
request can fail for a variety of reasons. If the -d8.1 (a.k.a. -d8) debugging switchis specified,
sendmail produces the following message:
getmxrr: res_search(host) failed (errno=errornum, h_errno=herrornum)
Here, host is the hostname that was looked up, errornum is the system error number (if
any) from
, and herrornum is the resolver-specific error number from ,
as shown in Table 15-6.
15.7.13 -d8.2
Call to getcanonname(3) Debug command-line switch
The routine dns_getcanonname( ) in domain.c of the sendmail source converts a hostname
to a fully qualified domain name. This routine is called only if DNS is used to look up hostnames,
as determined by the ResolverOptions option (?§24.9.98 on page 1080) and the
ServiceSwitchFile option (?§24.9.108 on page 1088). If it is, dns_getcanonname( ) can be
called from three places: during startup to get the values for $w, $j, and $m (?§15.7.2 on page
542); when a host is looked up via the $[ and $] canonify operators (?§18.7.6 on page 668);
or when a host is looked up using the host database map (?§23.7.9 on page 910).
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