Sendmail is defame for security holes. But this is also a fact that sendmail is one of popular MTA. Its not possible to avoid spamming through sendmail completely but yes sendmail can be configured in better way to limit spamming though it.
I am here discussing some of the options which can be useful in this context. Although this is a subjective discussion that these options are how much useful in different scenario.
is one of such option in sendmail.mc which specify number of Daemon’s children. But these children process can handle incoming and outgoing traffic both.
option specify how many queued message to process every time queue is run.
confQUEUE_LA andconfREFUSE_LA options are also very useful. confQUEUE_LA limit at what system load mail will queued for later processing and confREFUSE_LA specify at what load sendmail will reject will (Even will not queue for later processing).