If defined, LOG enables sendmail to use the syslog(3) facility to log error messages and other useful information that is often important for security and debugging. Logging and syslog(3) are described in Chapter 14. Defining LOG should be considered mandatory, and LOG should be turned off only if you have a well thought-out reason for doing so. LOG cannot be turned off in your Build m4 file. Instead, you must edit sendmail/conf.h directly and undefine it by commenting it out:

/* # define LOG           1          /* enable logging -- don't turn off */
  
comment out to remove support

The LOG compile-time macro requires that your system support syslog(3). If you lack syslog(3), consider porting it to your system.

Defining LOG is meaningless unless the LogLevel option (LogLevel) is also non-zero. Fortunately, this is usually the case because the default is 9. See also SYSLOG_BUFSIZE (SYSLOG_BUFSIZE) for a way to tune syslog(3)'s buffer size if necessary.

If you are running a precompiled sendmail binary, you can use the -d0.1 debugging command-line switch (-d0.1) to determine if LOG support is included (if it appears in the list, support is included). New ports should be reported to sendmail@sendmail.org so that they can be folded into future releases.