yes.  what exactly are you trying to do, i.e., why rotate your mailbox.
You'ld be better off with a pipeto that just sticks your mail into a
mailbox of the correct date in the first place.  Or you could just run
upas/fs and copy the raw files out into a mailbox and then remove them.
Something like:

	upas/fs
	cd /mail/fs/mbox
	x=`{echo *}
	> /whatever/mbox.$datum
	for(i in $x){
		{ cat $i/unixheader; cat $i/raw; echo }>>/whatever/mbox.$datum
		echo delete $i > /mail/fs/ctl
	}

Then at least you're safe, so to speak.