Potential host name conflict between name server and sendmail
In a DNS environment, a host name that is set using the hostname command from the command line or in the rc.net file format must be the official name of the host as returned by the name server.
Generally, this name is the full domain name of the host in the form:
host.subdomain.subdomain.rootdomain
Note: Resolver routines require the default domain to be set. If the default
domain is not set in the hostname command, then it must
be set in the /etc/resolv.conf file.
If the host name is not set up as a fully qualified domain name, and if the system is set up to use a domain name server in conjunction with the sendmail program, the sendmail configuration file (/etc/sendmail.cf) must be edited to reflect this official host name. In addition, the domain name macros in this configuration file must be set for the sendmail program to operate correctly.
Note: The domain specified in the /etc/sendmail.cf file
takes precedence over the domain set by the hostname command
for all sendmail functions.