Configuration Options to sendmail

Table B-2 includes all of the configuration options for sendmail. You can set them using the o flag when starting sendmail or by using the O line in the configuration file.

Use the Afile option to change the location of the alias file, which is normally set to /etc/mail/aliases.

You can reset the hop count using the h# option. The hop count determines the maximum number of hosts a particular message will be routed through before it is sent back to the sender. If a mail message gets into an alias loop, the hop count determines the number of hosts the message will try to go to before the message fails. The default hop count is set to 30, which may be too high for small domains or email domains that do not have many levels.

Two options can help control the system load. The X# option sets the maximum load average value and causes the daemon to refuse any incoming SMTP connections if the load average is above the value designated by #. You can increase the default value of 12, if the mail host can take the load. Using X0 refuses all SMTP connections.

The x# option queues the mail when the load average specified by # is reached instead of refusing it. Make sure that the server has enough disk space to hold all the queued mail before adjusting this value.

Both the options that work with the system load have a delay in response, so that restarting sendmail with new load average values does not immediately remedy all load problems.