SpamAssassin and the nonexistent home directory.

[Steve Bernacki]

Start spamd with -D (debug) on both servers to see where and how
spamassassin is configuring itself.  Chances are there is some subtle
configuration variation that is causing this behavior.  It's easy for this
to happen given the fact that spamassassin reads through a number of
directories for configuration information when it starts up.

Steve