Each time delivery is attempted
for a message, the number stored in its qf
file's N line is incremented by
one. This number always begins at zero.
When delivering many messages to a single host,
sendmail remembers failures. If one message
fails to make it all the way through an SMTP dialog, all the
following messages to that same host will be deferred (not attempted
during the current queue run). For those deferred messages the number
of tries is correctly incremented as though the delivery was actually
The value in this N line is used to determine
whether the delay of the MinQueueAge option (MinQueueAge) should be triggered. This value, when zero,
can also be used to enable a special first-time connection timeout
(See this section).