question

Hi everyone:
my MTA is sendmail8.9.3,the procmail as a local mail deliver agent can deliver 
mail to user's home directory,
but why i can not to receive mail by Outlook Express?

when i use qmail,mails also were deliverd to my user's home directory,
Outlook Express also can receive mail,this prove my pop3 has no problem
this maybe is not procmail problem,but i realy get lost,
please help me,that would be very kind of you