sendmail/flist problem

I installed procmail and SmartList, set up a mailing list and having a problem 
with sendmail:
 
sh: exec not available for sendmail programs
554 "|exec /home/slist/.bin/flist testing"... Service unavailable

 
I read through the FAQ, but I can't find what I am doing wrong. Please reply to 
me, oleg(_at_)inforocket(_dot_)com 
Thank you
Oleg