A few months ago I noticed that Mail’s search was broken, because searches within “Entire Message” always turned up nothing, altho searching Subject, From or To seemed to be working fine. After a little detective work I found out that uses Spotlight when searching Entire Message, so maybe Spotlight wasn’t indexing the mail folders? I tried forcing the issue with various utilities and the command line, but nothing seemed to work.

Today I tried using mdutil to turn on indexing for the main volume, and it worked! The command I used was
> sudo mdutil -i on /

So now Spotlight is happily chugging away, and it says it will be done in about twelve hours.

I don’t remember turning off Spotlight, but I can easily imagine turning it off “temporarily” (because indexing was slowing down something or other) only to forget all about turning it back on again. Ooo look, shiny!

Update: It only took about an hour to update, not twelve.