550 5.7.1. . . Relaying denied. IP name lookup failed Recently made a lot of email when abroad has always been rejected, and then to come back the following information missiles. 550 5.7.1+Relaying denied. IP name lookup failed[203.XXX] last firewall IP is IP, the mail server abroad. Who can help me this question, impatient. Thank you 195.XXX mail server for the IP, I would like to know which side in this issue out in the end. The other is the mail server, or our mail server problems. We are not a mail server and the relay list I did not join the side of the IP relay, a relationship. Up Ip address of the domain name you need to do is counter-analysis? Boss can specifically talk about? Analysis of the dark reverse themselves [ Closed window ]