Aliases to file

[Mark Gillingham <markgill@uwalumni.com>]

I want to set up a Postfix aliases entry to make it convenient for users
of another MTA (GroupWise) to send spam and ham for later entry to the
Bayes database via sa-learn. I have a Postfix server available and I've
made an entry to /etc/aliases (spam:  /var/spool/mail/spam/). When
Postfix attempts to save a mail file, I get the following error:

Jun 25 09:23:24 web2 postfix/local[12651]: 103814BE9D:
to=<spam@my.domain>, relay=local, delay=0, status=bounced (maildir
delivery failed: create
/var/spool/mail/spam/tmp/1088173404.12651_0.web2: Permission denied)

I've tried various directories, permissions, and owners including
/home/me/spam/ and /tmp/ with the same result.

/var/spool/mail/spam
drwxrwxrwt    3 root     mail         4096 Jun 25 09:21 spam

I tried making a tmp dir within spam with this acl:
drwxrwxr-x    2 root     mail         4096 Jun 25 09:21 tmp

Perhaps I need to use mbox format rather than trying to use maildir?
Ideas? tia

Mark