12.3. Local Delivery Errors

Remote deliveries are not the only cases where a temporary error may be encountered; they can also arise during local deliveries. The two most common cases are as follows:

• A delivery to a mailbox file fails because the user is over quota.

• A delivery to a command via a pipe fails, with the command yielding a return code that is defined as "temporary" (see Section 9.6 in Chapter 9).