When the load average on a machine (the average number of processes in the run queue over the last minute) becomes too high, sendmail can try to compensate by queuing all mail rather than delivering it. The QueueFactor option is used in combination with the QueueLA option (QueueLA) to calculate the point at which sendmail stops delivering. If the current load average is greater than or equal to the value given to the QueueLA option, the following formula is evaluated:

msgpri > q / (la - x + 1)

Here, q is the value set by this option, la is the current load average, and x is the cutoff load specified by the QueueLA option. If the value yielded by this calculation is less than or equal to the priority of the current mail message (msgpri in this example), the message is queued rather than delivered. Priorities are initialized with the P sendmail.cf command (Section 25.10) and tuned with the RecipientFactor and ClassFactor options (RecipientFactor). As the load average (la) grows, the value to the right of the > becomes smaller, increasing the chance that msgpri will exceed that threshold (so that the mail will be queued).

The forms of the QueueFactor option are as follows:

O QueueFactor=fact             configuration file (V8.7 and later) 
-OQueueFactor=fact             command line (V8.7 and later) 
define(`confQUEUE_FACTOR',fact)    mc configuration (V8.7 and later) 
Oqfact                         configuration file (deprecated) 
-oqfact                        command line (deprecated) 

The argument fact is of type numeric. It can be positive, negative, or zero. If fact is missing, the value defaults to zero. If the entire QueueFactor option is missing, the default value given to fact is 600000 (six hundred thousand). The default for the mc technique is to omit this option.

Note that the load average is effective only if your sendmail binary was compiled with load-average support (LA_TYPE), which is highly probable. Use the -d3.1 debugging switch to discover whether your binary includes that support.

The QueueFactor option is not safe. If specified from the command line, it can cause sendmail to relinquish its special privileges.