10.3.9 Mail – Hot Copy Backup Via Rsync Advisable?

I have a 10.3.9 server running mail services, including the MAILTRANSPORT spam/virus filtering apparatus devised by AFP548. Our mail services turn off each morning at 2:30 to rsync the data stores for Postfix and Cyrus to a backup volume. It takes around 45 minutes to complete, which means we're not receiving e-mail during this time. Other MTAs will just try to deliver mail to us again later. However, we have a bunch of websites that send order acknowledgment e-mails when an order is placed. If our mail services are off, these acknowledgments are lost forever. I'm wondering if I can get away with rsyncing these data stores while mail services are still running. Opinions?