This is the SMTP RULES keyword. When SMTP parses the rule in message EZA5393I, each string in the keyword is displayed along with one of these messages. As indicated, the specific message you see depends on whether the string is case-sensitive and whether it is a wildcard. Some keywords have special meaning to the rules interpreter. For more information, see z/OS Communications Server: IP Configuration Reference. See also message EZA5416E.