Mail domain name – If you are setting up NIS+ as your primary name service, sendmail can check the mail domain from the NIS+ sendmailvars table. This NIS+ table has one key column and one value column. To set up your mail domain, you must add one entry to this table. This entry should have the key column set to the literal string maildomain and the value column set to your mail domain name. An example is admin.acme.com. Although NIS+ allows any string in the sendmailvars table, the suffix rule still applies for the mail system to work correctly. You can use nistbladm to add the maildomain entry to the sendmailvars table. Notice in the following example that the mail domain is a suffix of the NIS+ domain.
nistbladm -A key="maildomain" value=<mail domain> sendmailvars.org_dir.<NIS+ domain>
Mailhost host name – If your network uses both NIS+ and DNS as the source for the host database, you can put the mailhost entry in either the NIS+ or DNS host table. Ensure that your users include both NIS+ and DNS as the source for the host database in the /etc/nsswitch.conf file.
Full host names – Both NIS+ and DNS “understand” full host names. Following the regular NIS+ and DNS setup procedures satisfies this requirement.
Matching full host names and short host names – For every host entry in the NIS+ host table, you must have a corresponding host entry in DNS.
Multiple NIS domains in one mail domain – To satisfy this requirement, you can duplicate the entries in all the host tables. Alternately, you can type all host entries in the user name-service domains into a master host table at the mail domain level.