5.3 RC2 sendmail problem

[Nick Sayer]

Something is very wrong with sendmail in 5.3RC2.

Under 5.2.1, my sendmail config, which is simply the default, plus a 
SMART_HOST worked fine. Under 5.3RC2, attempts to get to the smart host 
result in 'host name lookup failure'.

In searching the archives, I note I am not the first to bring this up, 
but I've found no solution.

I'm really, really sure nothing changed except upgrading to 5.3RC2. 
What happened?