The MAILER() declaration specifies support for delivery agents. To declare a delivery agent, use the following syntax.
MAILER(`symbolic-name')
Note the following changes.
In this new version of sendmail, the MAILER(`smtp') declaration now includes an additional mailer, dsmtp, which provides on-demand delivery by using the F=% mailer flag. The dsmtp mailer definition uses the new –DSMTP_MAILER_ARGS, which defaults to IPC $h.
Numbers for rule sets that are used by MAILERs have been removed. You now have no required order for listing your MAILERs except for MAILER(`uucp'), which must follow MAILER(`smtp') if uucp-dom and uucp-uudom are used.
For more information about mailers, refer to Mailers and sendmail. If you need to build a new sendmail.cf file, refer to Changing the sendmail Configuration in Chapter 2, Administering Mail Services.