What exactly is the sm-client service and when is it used?

Question

When I restart Sendmail services, I see the following:

[root@foo ~]# service sendmail restart
Shutting down sm-client:                                   [  OK  ]
Shutting down sendmail:                                    [  OK  ]
Starting sendmail:                                         [  OK  ]
Starting sm-client:                                        [  OK  ]

What exactly is sm-client? The bat book doesn't mention it in much detail.

Solution

Before sendmail-8.12 sendmail had used to a set root uid program. It had created constant stream of security exploits/dangers.

Starting with sendmail-8.12 sendmail is not installed as set root uid by default.

• Sendmail is installed set set group program. Sendmail executed by a non privileged user passes email to 127.0.0.1:25 where "classic" sendmail daemon running with root privileges waits to process it.
• sm-client daemon processes messages (queued in special/separate queue directory) which have failed the above step. It may be replaced by periodic cron jobs.

http://www.sendmail.org/~ca/email/doc8.12/SECURITY