New Rule or Block System.
When sender try to send using ip and not domain block.
Sample LOG:
SMTP-IN 72D0F85EDEE.MAI 2952 59.18.131.33 HELO HELO 188.164.192.64 250 Requested mail action okay, completed 43 21
SMTP-IN 72D0F85EDEE.MAI 2952 59.18.131.33 MAIL MAIL FROM: <Wilkes_Suzanne@bhagwatiindustries.com> 250 Requested mail action okay, completed 43 52
SMTP-IN 72D0F85EDEE.MAI 2952 59.18.131.33 RCPT RCPT TO: <sample@sample.com> 554 This server requires PTR for unauthenticated connections. 63 37
SMTP-IN 72D0F85EDEE.MAI 2952 59.18.131.33 QUIT QUIT 221 Service closing transmission channel 42 6
Block ip 59.18.131.33