Delivery Mode

The Od option in the configuration file sets the delivery mode. The default delivery mode is Odbackground. Delivery modes specify how quickly mail is delivered. Table 3-3shows the legal modes.

Table 3-3 Delivery-Mode Options

Code	Description
i	Delivers interactively (synchronously)
b	Delivers in background (asynchronously)
q	Queues only (does not deliver)

There are trade-offs. The interactive mode (i) passes the maximum amount of information to the sender, but it is seldom necessary. The queue mode (q) puts the minimum load on your machine, but means that delivery might be delayed for up to the queue interval. The background mode (b), the default, is a good compromise.