Fix my email sending issue with MailWizz

Hi, I need someone with strong skills with DNS and MailWizz newsletter sending application. Here is my issue: I have a MailWizz installation on DigitalOcean to send newsletters. I'm also using my domain with Zoho mail. I'm also using an SMTP delivery service. My problem is that some of my emails are not delivered to certain email service providers, like [login to view URL], or [login to view URL] I'm getting errors like this: This is the mail system at host imprevo.smtp.hu. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. The mail system <kispet*****1@[login to view URL]>: host [login to view URL][[login to view URL]] said: 550 5.7.1 Message denied by policy. gggruggvucft... (in reply to end of DATA command) Reporting-MTA: dns; [login to view URL] X-Postfix-Queue-ID: 4E94A5A00F7 X-Postfix-Sender: rfc822; bounce@[login to view URL] Arrival-Date: Fri, 22 Jun 2018 13:15:04 +0200 (CEST) Final-Recipient: rfc822; kis****91@[login to view URL] Original-Recipient: rfc822;kis****91@[login to view URL] Action: failed Status: 5.7.1 Remote-MTA: dns; [login to view URL] Diagnostic-Code: smtp; 550 5.7.1 Message denied by policy. gggruggvucftvghtrhhouc Return-Path: <bounce@[login to view URL]> Received: from [login to view URL] (unknown [[login to view URL]]) by [login to view URL] (Postfix) with ESMTPA id 4E94A5A00F7 for <kis****91@[login to view URL]>; Fri, 22 Jun 2018 13:15:04 +0200 (CEST) Message-ID: <d9f369bb9c6c811136db142a40357516@[login to view URL]> Date: Fri, 22 Jun 2018 11:15:02 +0000 Subject: Angol levelek =?utf-8?Q?=C3=A9s?= emailek =?utf-8?Q?=C3=ADr=C3=A1sa_let=C3=B6lt=C3=A9s?= - Itt az ingyenes Ebookod From: Adam =?utf-8?Q?F=C3=BCl=C3=B6p?= <info@[login to view URL]> Reply-To: Adam =?utf-8?Q?F=C3=BCl=C3=B6p?= <info@[login to view URL]> To: "kis****91@[login to view URL]" <kis****791@[login to view URL]> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="_=_swift_v4_1529666102_46e656c8f70fe833cee657f386ee3130_=_" X-Sender: bounce@[login to view URL] X-Report-Abuse: Please report abuse for this campaign here: [login to view URL] X-Receiver: kis****91@[login to view URL] X-Byfv-Tracking-Did: 0 X-Byfv-Subscriber-Uid: bt76007p6mb65 X-Byfv-Mailer: SwiftMailer - 5.4.x X-Byfv-EBS: [login to view URL] X-Byfv-Delivery-Sid: 2 X-Byfv-Customer-Uid: gc526lnaxjeab X-Byfv-Customer-Gid: 0 X-Byfv-Campaign-Uid: eo531vtodcc41 Precedence: bulk List-Unsubscribe: <[login to view URL]>, <mailto:info@[login to view URL]:eo531vtodcc41 / Subscriber-Uid:bt76007p6mb65 - Unsubscribe request&body=Please unsubscribe me!> List-Id: al435cxj6856d <Angol levelek =?utf-8?Q?=C3=ADr=C3=A1sa=3E?= Feedback-ID: eo531vtodcc41:bt76007p6mb65:al435cxj6856d:gc526lnaxjeab Please only apply if you are certain that you can fix this issue.