Ok, figured it out.
It is a spamassassin config issue - so sorry about the post on this list.
Not sure why I couldn't find it earlier when I was searching Google.
Anyway - this link has the details:
----- Original Message -----
From: "Myron Davis" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, April 12, 2004 1:14 PM
Subject: Re: [vchkpw] no such users direcotries - help
> Try changing your mailfilter script around to filter for "no such user",
> i.e. look at:
> > I'm using VpopMail 5.2.1 , and i've recently noticed a whole bunch of
> > such user [EMAIL PROTECTED]" directories in my root partition. i have
> > that are for real users of virtual domains i'm hosting and i have some
> > addresses of emails i've sent out to people. inside the folder is
> > nothing, if i delete them they come back. any idea what this is and why
> > they are being created?
> > thanks for the help!