Time Values

All time intervals use a syntax of numbers and letters. For example, 10m is 10 minutes, and 2h30m is two and one-half hours.

Table 3-2 lists the time symbols.

Queue Interval

The argument to the q flag specifies how often sendmail runs the queue. It is usually set to between 15 minutes (q15m) and 1 hour (q1h).

Read Timeouts

The Or option in the configuration file sets the read timeout. The default read timeout is Or15m. Although it is technically unacceptable within the published protocols, sendmail might time out when reading the standard input or when reading from a remote SMTP server. If your site has problems with read timeouts, set the read timeout to a larger value, like one hour (Or1h), to reduce the chance of several idle daemons piling up on your system.

Message Timeouts

The OT option in the configuration file sets the message timeout. The default message timeout is three days (OT3d). After a message has been in the queue for the message time-out period, the sender is notified that the message could not be delivered.

You can flush messages that have been hanging for a short period by running the queue with a short message timeout. For example, the command

# /usr/lib/sendmail -oT1d -q

runs the queue and flushes any message that is one day old or older.