How do I restore smart mailboxes after upgrade to El Capitan from 10.6?

I upgraded a 2012-era MacBook Pro from 10.6 directly to El Capitan. After the upgrade, everything seems to be working fine except for Smart Mailboxes. The old messages are there when I search for them, but the Smart Mailbox rules and the Smart Mailboxes themselves are gone. Is there an easy way to restore them other than to re-write all of the Smart Mailbox rules? Thanks.