Keep Sendmail Happy is a StartupItem that fixes the permissions on /, /etc and /etc/mail so that Sendmail (as distributed with 10.1.4 at least) will run.
To install it, log in as an administrator and copy the folder KeepSendmailHappy into /Library/StartupItems. If your system doesn't have /Library/StartupItems, go ahead and make it, but make sure you get the spelling correct.
What's new in Keep Sendmail Happy X
Version 0.1.4 was released again with MacOS X 10.1.5 support.