When you update a major system, you have to expect little drawbacks - but hopefully you catch them sooner than this! Last friday we patched a major server running Solaris - upgraded all of its packages, etc. Including Sendmail. Well, this blew away the sendmail NIS settings and thus the aliases file - root mail was only going to one person, and nothing else was set for any of our users' aliases! We checked into it a bit, and from what I can tell, Sendmail just added a hardcoded setting to look for the aliases file in ONE PLACE, basically ignoring all others, including the NIS files. It also made that place its own folder, and helpfully provided a file for us - a default file - with only one alias for root and none other. Oh joy.

Fix? soft-linked the NIS aliases file to the /etc/mail folder where sendmail expected to see the aliases file, and ran newaliases to generate the db-style files sendmail needs. Fun.