Article ID: 5269, created on May 21, 2008, last review on May 10, 2014

  • Applies to:
  • Plesk


SMTP service goes away for a random amount of time and customers cannot send mail, /var/log/messages shows:

xinetd[10714]: Deactivating service smtp due to excessive incoming connections.  Restarting in 30 seconds.
xinetd[10714]: Activating service smtp


Such messages are caused by xinetd access restrictions that are defined in the  /etc/xinetd.conf. For example:

        cps             = 50 10
        instances       = 50
        per_source      = 10

'cps' value  limits the rate of incoming connections. Takes two arguments.  The first argument is the number of connections  per second  to  handle.   If  the rate of incoming connections is higher than this, the service will be temporarily disabled.  The second argument is the number of seconds to wait before re-enabling the service after it has  been  disabled.  The default for this setting is 50 incoming connections and the interval is 10 seconds.

'instances' determines the number of servers that can be simultaneously active for a service.

'per_source' specifies the maximum number of instances of the service per source IP address.


If you feel that the default values are not enough for the server, you can increase them by editing /etc/xinetd.conf and restart xinetd then.

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