O-Set Option

You can set several options (not to be confused with mailer flags or command-line arguments) from a configuration file. Options are also represented by single characters. The syntax of this line is:

Oc value

This sets option c to value. Depending on the option, value may be a string, an integer, a Boolean (with legal values t, T, f, or F--the default is "true''), or a time interval. See "Configuration Options to sendmail" for the list of options.