>>> check hosts = 1.2.3/24
>>> host in "1.2.3/24"?
>>> list element: 1.2.3/24
->>> host in "1.2.3/24"? no (malformed IPv4 address or address mask)
+>>> host in "1.2.3/24"? no (malformed IPv4 address or address mask: 1.2.3)
>>> deny: condition test failed in ACL "a2"
>>> end of ACL "a2": implicit DENY
LOG: H=(test) [V4NET.0.0.0] F=<> rejected RCPT <a2@b>