Donna,
  On a Un*x box, I'd head for the newaliases command which rebuilds aliases.db
from /etc/aliases.  I think that the error is triggered when /etc/aliases
has been changed since aliases.db, but I don't know for sure.  If newaliases
is not in evidence, you can try

sendmail -bi

HTH,
Ted
--
Ted Ashton ([log in to unmask]), Info Serv, Southern Adventist University
          ==========================================================
What vexes me most is, that my female friends, who could bear me very well a
dozen years ago, have now forsaken me, although I am not so old in
proportion to them as I formerly was: which I can prove by arithmetic, for
then I was double their age, which now I am not.
                        -- Swift, Jonathan