30% failure rate with sieve? debug output...?

[Jo Rhett]

So I *finally* got my employers out of stone-age multihundred  
megabyte inbox files and over to cyrus.  Yay!

However, we're seeing fairly consistent sieve failures.  For example,  
21 messages came from a certain address that we're filtering last  
night.  12 were filed into the subfolder correctly.  4 fell down and  
hit a later rule in the ruleset, and 5 made it into my inbox.   
Grepping through the logs (at debug level) indicates zero complaints  
from sieve.

So... clue me in.  How do I get real debugging enabled?  I want very  
verbose output stored somewhere so that I can analyze the failures...

-- 
Jo Rhett
Senior Network Engineer
Network Consonance