Getting flooded by incoming spam? Try these settings:
Setting the maximum number of Sendmail processes
define(`confMAX_DAEMON_CHILDREN',7)
Limit connection time of incoming connections
define(`confTO_ICONNECT',`10s')
define(`confTO_DATABLOCK',`5m')
This will stop spam/misconfigured hosts for keeping connections open for a long time.
Add these to /etc/mail/sendmail.mc, and restart Sendmail: /etc/init.d/sendmail restart
Thanks to Don Wallace (a RimuHosting customer) for these handy tips.