# Check the /usr/share/doc/sendmail/README.cf file for a description
# of the format of this file. (search for access_db in that file)
# The /usr/share/doc/sendmail/README.cf is part of the sendmail-doc
# package.
#
# by default we allow relaying from localhost...
localhost.localdomain		RELAY
localhost			RELAY
127.0.0.1			RELAY
first.relay.from.ip		RELAY
second.relay.from ip		RELAY


Put these in a simple to format. Once done run the command:

makemap hash /path/to/access < path/to/access

Access being the filename to use or whatever you used in your
sendmail.mc file.