maildrop: (user unknown. Command output: Invalid user specified. )

[blueflametuna]

Trying to setup Postfix/Courier/Maildrop/Pop3 with TLS/SSL and SMTP AUTH
on Fedora Core 4...

The log says:

postfix/pipe[12061]: 1F1561B74034: to=<testpop@homebydesign.com>,
orig_to=<testpop>, relay=maildrop, delay=21, status=bounced (user
unknown. Command output: Invalid user specified. )

In master.cf:

maildrop unix - n n - - pipe
flags=DRhu user=courier argv=/usr/local/courier/bin/maildrop -d
${recipient}

Is the error due to the user "testpop" or "courier"?
If the latter, then is that because courier is not compiled in as a
trusted user?

Thanks!