sendmail, 4th Edition

DeliveryMode

Set delivery mode All versions

sendmail can use four modes for delivering mail. Three have always been a part of sendmail: background, interactive, and queue-only. The deferred mode has been added under V8.7 and later sendmail.

The mode is selected with the DeliveryMode option:

O DeliveryMode=mode                ← configuration file (V8.7 and later)
-ODeliveryMode=mode                ← command line (V8.7 and later)
define(`confDELIVERY_MODE',mode)   ← mc configuration (V8.7 and later)
Odmode                             ← configuration file (deprecated)
-odmode                            ← command line (deprecated)

The mode argument is of type character. It is case-sensitive (must be lowercase) and is selected from one of the keywords shown in Table 24-16. Only the first letter of each is recognized, but we recommend full words for improved clarity.

Table 24-16. DeliveryMode option keywords

Keyword	§	Description
background	DeliveryMode=background on page 1005	Background (asynchronous) delivery
deferred	DeliveryMode=deferred on page 1006	Deferred (held as is) delivery (V8.7 and later)
interactive	DeliveryMode=interactive on page 1006	Interactive (synchronous) delivery
queueonly	DeliveryMode=queueonly on page 1006	Queued (held but processed) delivery

If the mode argument is missing, this option defaults to the i or interactive mode. If the entire DeliveryMode option is missing, V8 sendmail defaults to background mode, but old sendmail behaves unpredictably; consequently, this option should be considered mandatory. The default for the mc configuration ...