Yesterday morning I upgraded to firmware version 9.705-7. This morning at about 6:00 am the RBL feature has started rejecting well-known hosts. Shown here are oktax.state.ok and pharmacy.cvs.com.
Checking pharmacy.cvs.com with www.anti-abuse.org I see that it's all green.
I have turned off the RBL checks in the SMTP Antispam page and those email addresses are now going through the mail server.However, so are any 'bad-guy' sites that actually test as RBL failures. So, this is a workaround, not a fix.