After rebooting sendmail servers, internal servers must fully qualify for mail

[Christopher]

Help anyone?

We rebooted our sendmail servers, and now all of our internal servers need
FQDN when sending mail.
Example:
Old way(what we want again):  blah na domain.net
new way: blah na mail.zone.domain.net

What controls that?  Is this a sendmail issue?  No changes were made to DNS.
Any help would be appriciated!  Thanks!