Since past few days, I am not able to send email to any person one specific domain, I would call it xyxyxyxy.org. I am not sure if some changes were done on our network side or recipient's side.
When I sent test email from my unix server, I can see below message on /var/log/maillog
Jan 3 14:36:37 mail-relay-server postfix/smtp: CA0BA102B6E4: email@example.com, relay=smtp1.xyxyxyxy.org[220.127.116.11]:25, delay=0.06, delays=0.01/0/0.05/0, dsn=4.0.0, status=deferred (host smtp1.xyxyxyxy.org[18.104.22.168] refused to talk to me: 554 No SMTPd here 202201032236360132090;12)
And this test too
[root@mail-relay-server ~]# telnet smtp1.xyxyxyxy.org 25
Trying 22.214.171.124... Connected to smtp1.xyxyxyxy.org. Escape character is '^]'. 554 No SMTPd here 202201032250260132555;12 Connection closed by foreign host. [root@mail-relay-server ~]# telnet smtp2.xyxyxyxy.org 25 Trying 126.96.36.199... Connected to smtp2.xyxyxyxy.org. Escape character is '^]'. 554 No SMTPd here 202201032250310278916;10 Connection closed by foreign host. [root@mail-relay-server ~]#
Does it mean that recipient's domain is rejecting our mail and I should follow with them or something could be on our network or our mail server? All other emails and external emails are going as it is.