An expensive mailer is a delivery agent that contains an e flag in its F= equate (F=e). Typically, such delivery agents are associated with slow network connections such as SL/IP, or with costly networks such as those with high per-connect or connection startup rates. Whatever the reason, the HoldExpensive option allows you to queue all such mail for later delivery rather than connecting on demand. (Queuing is described in Chapter 11.)

Note that this option affects only the initial delivery attempt, not later attempts when the queue is processed. Essentially, all this option does is to defer delivery until the next time the queue is processed.

The forms of the HoldExpensive option are as follows:

O HoldExpensive=bool            configuration file (V8.7 and later) 
-OHoldExpensive=bool            command line (V8.7 and later) 
define(`confCON_EXPENSIVE',bool)    mc configuration (V8.7 and later) 
-c                              command-line shorthand (not recommended) 
Ocbool                          configuration file (deprecated) 
-ocbool                         command line (deprecated) 

The argument bool is of type Boolean. If the bool argument is missing, the default is true (expensive mail is queued). If the entire HoldExpensive option is missing, the default value is false (expensive mail is delivered immediately).

The -v (verbose) command-line switch automatically sets the HoldExpensive option to false. The HoldExpensive option is not safe. If specified from the command line, it can cause sendmail to relinquish its special privileges.