xfilter timeout?

I've recently been rebuilding my mail environment, and finally pushing procmail
out in favor of maildrop.  (I know, I know.  I'm waaay more than a little late
to the game.  :)

Running into a wall.  Specifically, any use of xfilter seems to timeout.

The entirety of my .mailfilter is as follows:


    SHELL="/bin/sh"
    DEFAULT=$HOME/Maildir
    LOGFILE=$HOME/maildrop.log

    logfile "$LOGFILE"

    xfilter "/bin/cat"


My understanding of this config is that the message should pass through 'cat'
unmolested, and delivered to $DEFAULT.

Upon new incoming mail, the maildrop process appears to just... hang out, until
it gets a timeout.  They stack up.

    mahlon   30754  0.0  0.0   18032   5356  -  IJ   15:37      0:00.01 /usr/local/bin/maildrop
    mahlon   31352  0.0  0.0   17844   5240  -  IJ   15:38      0:00.01 /usr/local/bin/maildrop
    mahlon   31380  0.0  0.0   17844   5240  -  IJ   15:38      0:00.01 /usr/local/bin/maildrop


If I comment out the xfilter, it delivers instantly. This is using Maildrop
3.1.5, using (net)qmail on FreeBSD 13.1.  My qmail delivery instructions are
simply:

    | /usr/local/bin/maildrop

Final message is:  "maildrop: Timeout quota exceeded."

I can't escape the feeling that I am doing something patently silly here, but
I'm just not seeing it.  I appreciate any cluebats to be bludgeoned with, or
hints on how to provide better debug.

Thanks!

-- 
Mahlon E. Smith  
http://www.martini.nu/