> On May 1, 2018, at 10:38 AM, Fazzina, Angelo <angelo.fazz...@uconn.edu> wrote:
>
> Hi, okay that makes sense.
>
> I guess my next question is what is going on when we get a bulk mail campaign
> or spam attack and I see the /var/spool/postfix/incoming
> Directory only allow 20,000 files in there ?
It is the "active" queue that qmgr(8) avoids filling with too many messages
at once, because each *active* message requires memory for scheduler metadata.
The incoming queue will grow (almost) as large as the filesystem permits, but
once the queue manager is no longer keeping up some SMTP sessions will incur
the inflow-delay (but this does not prevent input from running faster than
output, rather it keeps the amount by which input *exceeds* output to at most
input concurrency / inflow_delay.
If you allow 100 parallel SMTP sessions, and have a 1s inflow delay, then
the input rate can *exceed* the output rate by 100 msgs/sec. If that
goes on for long enough, your incoming queue will get rather large, but
only your filesystem space will cap that, not any hard-limit in Postfix.
--
Viktor.
