Chapter 24. The O (Options) Configuration Command
Options affect the operation of the sendmail program. Options can be specified in the command line, in the sendmail.cf file, and in the mc configuration file. Options can change, tune, or affect:
Locations of all the other files that sendmail needs to access, such as the aliases file.
Locations of queue directories and the use of queue groups.
Time limits that should be applied to the TTL in the queue, the length of time to wait for an SMTP connection, and so on.
Default permissions for files and the default user and group identities to use when not running as another user.
Degree of privacy desired, such as what kinds of inquiry to reject or who can examine the queue.
Modes of behavior, such as always queuing or running as a daemon and listening for incoming connections.
Limits that should be placed on system resources. Should one queue only under high load? Should one reserve minimal space in the queue?
Small bits of sendmail’s behavior, such as allowing colons to appear in addresses and stripping newlines from sender addresses.
Most options are preset in your sendmail.cf file to be appropriate for your site. Those that need local definitions will usually be indicated by comments. Some sites, especially those that have high mail loads or those connected to many different networks, will need to tune many of the options according to their unique needs.
 These comments do not mean that you should change options by editing your ...