sendmail, 4th Edition

-d0.4

Our name and aliases Debug command-line switch

The -d0.4 debugging switch tells sendmail to print several lines of information in addition to those printed by -d0.1:

Version 8.14.1
Compiled with:   LOG MATCHGECOS NAMED_BIND NDBM NEWDB NETINET NETUNIX
                 NIS
canonical name: here.US.EDU                            ← additional
UUCP nodename: here                                   ← additional
        a.k.a.: [123.45.67.89]                         ← additional
=  ==  ==  ==  ==  ==  = SYSTEM IDENTITY (after readcf) =  ==  ==  ==  ==  ==  =
            (short domain name) $w = here
        (canonical domain name) $j = here.US.EDU
               (subdomain name) $m = US.EDU
                    (node name) $k = here
=  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==  ==
 ==  ==  ==  ==  ==  ==  =

To find the canonical name of the local host, sendmail calls gethostname( ). If that call fails, the name localhost is used. The hostname is then looked up with the internal routine sm_gethostbyname( ), which gathers additional information (such as other names and addresses for the machine) and fixes several bugs in some operating system versions of the gethostby... routines. Next the canonical name for the local host is looked up. For operating systems that normally support switched services, the name is looked up as specified. For systems that specify switched services in the configuration file’s ServiceSwitchFile option (ServiceSwitchFile on page 1088), switched services are not used because the configuration file has not been read yet. (This canonicalization process can be traced with the -d61.10 debugging switch.) If the canonical name is found ...