2.2.8. Securing Sendmail
18.104.22.168. Limiting a Denial of Service Attack
/etc/mail/sendmail.mc, the effectiveness of such attacks is limited.
confCONNECTION_RATE_THROTTLE— The number of connections the server can receive per second. By default, Sendmail does not limit the number of connections. If a limit is set and reached, further connections are delayed.
confMAX_DAEMON_CHILDREN— The maximum number of child processes that can be spawned by the server. By default, Sendmail does not assign a limit to the number of child processes. If a limit is set and reached, further connections are delayed.
confMIN_FREE_BLOCKS— The minimum number of free blocks which must be available for the server to accept mail. The default is 100 blocks.
confMAX_HEADERS_LENGTH— The maximum acceptable size (in bytes) for a message header.
confMAX_MESSAGE_SIZE— The maximum acceptable size (in bytes) for a single message.