Some errors in local delivery are considered transient. For example,
if the mail.local tries to open a
user's mailbox file, and that open fails because the
user's mailbox is already larger than is permitted,
delivery will fail. In such a failure, the mail is ordinarily left in
the sendmail queue awaiting another try later.
On systems with limited resources, it is sometimes better to take a
firm stand and disallow any file that exceeds the
user's quota. You do this with
mail.local by adding a -b
define(`LOCAL_MAILER_ARGS', `mail.local -l -b')
See the Unix online manual page concerning
quota(1) for information about limiting
users' use of disk resources and about why this
error will occur.