about two weeks ago I had security breach, one mail account on server, caused outgoing spam, I got listed in on couple blacklists rbl. Problem was fixed, IP was removed from all black lists. I can't still mail to google servers (gmail 550-5.7.1 likely unsolicited mail). Problem applies only one of domains on server, from rest domains on the same machine, mails are delivering without problems to gmail servers. Look this, test from one server, outgoing mail from two domains:
Reporting-MTA: dns; ns3481305.ip-176-31-231.eu X-Postfix-Queue-ID: 2CC23222C6 X-Postfix-Sender: rfc822; email@example.com Arrival-Date: Mon, 30 Jan 2017 07:56:39 +0100 (CET)
Final-Recipient: rfc822; ....com Original-Recipient: rfc822;... Action: failed Status: 5.7.1 Remote-MTA: dns; gmail-smtp-in.l.google.com Diagnostic-Code: smtp; 550-5.7.1 [2001:41d0:2:f8eb:: 12] Our system has detected that this message 550-5.7.1 is likely unsolicited mail. To reduce the amount of spam sent to 550-5.7.1 Gmail, this message has been blocked. Please visit 550-5.7.1 more information. k46si15331100wrk.55 - gsmtp
Second test from same server, mail delivered no problem:
Delivered-To: ... Received: by 10.12.180.171 with SMTP id c43csp1297317qve; Mon, 30 Jan 2017 00:05:23 -0800 (PST) X-Received: by 10.28.178.142 with SMTP id b136mr13272598wmf.69.1485763523027; Mon, 30 Jan 2017 00:05:23 -0800 (PST) Return-Path: Received: from ns3481305.ip-176-31-231.eu ([2001:41d0:2:f8eb::]) by mx.google.com with ESMTP id m15si12383431wmh.131.2017.01.30.00.05.22 for ; Mon, 30 Jan 2017 00:05:22 -0800 (PST) Received-SPF: pass (google.com: domain of firstname.lastname@example.org designates 2001:41d0:2:f8eb:: as permitted sender)
Server is not currently blacklisted: http://www.anti-abuse.org/multi-rbl-check-results/?host=126.96.36.199 http://mxtoolbox.com/SuperTool.aspx?action=blacklist:188.8.131.52
SPF, DKIM and rDNS are configured, everything worked while got security breach and spam accident.