Hello Community!!
We are experiencing the following error on our server. One client is trying to send over mail, but the mails are not even received by the server. When we inspected the logs we get the following errors:

Sep 22 04:15:39 mail postfix/smtpd[29208]: connect from mail.client.com[x.x.x.x]
Sep 22 04:15:39 mail postfix/smtpd[29208]: warning: milter inet:127.0.0.1:10027: can't read SMFIC_UNKNOWN reply packet header: Success
Sep 22 04:15:39 mail postfix/smtpd[29208]: NOQUEUE: milter-reject: UNKNOWN from mail.client.com[x.x.x.x]: 451 4.7.1 Service unavailable - try again later; proto=SMTP

Anybody had this issue before?? Please any howto on solving this???

Thanks in advance!!!