Where does mail info come from in finger ?

[tibor szikszai]

I looked at the source for finger, but I couldn't find anything that
seems to be checking any files for whether the person being fingered
has mail or not.  So I am curious about how things like "No unread
mail." or "New mail received ...  Unread since ..." or "Mail last read ..."
get printed.  Does anybody know?  Is another daemon doing this job?