detecting failure to chdir() to $MAILDIR

I wanted procmail to fail temporarily if my maildir wasn't accessible,
so I tried this:

    EXITCODE    = $EX_TEMPFAIL
    MAILDIR     = /oldbox/roderick/inbox
    EXITCODE

I figured that procmail would exit if the chdir() failed, but it didn't,
it just logged

    procmail: Couldn't chdir to "/oldbox/roderick/inbox"

and continued processing the configuration file.  Now I'm using

    MAILDIR = /oldbox/roderick/inbox
    :0
    * ? test x-"`pwd`" != x-"$MAILDIR"
    { EXITCODE = $EX_TEMPFAIL HOST }

and I think this works.  This will fail if a symlink creeps into that
path, though.

Is there a better way?

-- 
Roderick Schertler
roderick(_at_)argon(_dot_)org