If your site wants nothing to do with UUCP addresses, you can set the nouucp feature. Among the changes this causes are that the ! character is not recognized as a separator between hostnames, and all the macros that relate to UUCP (Section 4.6) are ignored. This feature truly means no UUCP.

You declare nouucp like this:

FEATURE(`nouucp')            through V8.9
FEATURE(`nouucp',`nospecial')    V8.10 and above
FEATURE(`nouucp',`reject')   V8.10 and above

Beginning with V8.10 an argument has been added that can either be nospecial or reject. The nospecial causes sendmail to simply ignore the ! character. The reject causes sendmail to reject mail with the ! character. If you declare neither argument (as in the first line), and you are using sendmail V8.10 or above, you will see the following error, and your configuration file will fail to build properly:

*** ERROR: missing argument for FEATURE(nouucp):
                use `reject' or `nospecial'. See cf/README.

Note that all the other UUCP declarations (such as UUCP_RELAY) will be ignored if you use this nouucp.

When you use this feature on any machine that forwards uucp mail to a central mail hub machine, be certain that you also declare it on that mail hub machine. If you don't take this precaution, you open up your mail hub to risk of unintended relaying.