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Richard, Email Systems Specialist
Category: Email
Satisfied Customers: 36526
Experience:  Over 15 year experience in Email Systems and Programs
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Diagnostic-Code: smtp; 550 5.7.0 (COL004-MC5F9) Message

Customer Question

Diagnostic-Code: smtp; 550 5.7.0 (COL004-MC5F9) Message could not be delivered when sending to hotmail address
JA: How long have you had this issue with your Hotmail account?
Customer: it went fine for years, but since 3 to 4 weeks i got those issues
JA: How do you access your email most often? On a phone or tablet, or through a web browser?
Customer: it's a web server sending the mail because a club member registered for a course
JA: What troubleshooting have you tried?
Customer: checked all logfiles, had a look at the mail source code inclusive all header lines
JA: Anything else you want the email expert to know before I connect you?
Customer: nothing particular...
Submitted: 9 months ago.
Category: Email
Expert:  Josh replied 9 months ago.

Hi! My name is ***** ***** I will be assisting you. Let's get started!

Expert:  Josh replied 9 months ago.

Are you using an email program?

Is it happening to multiple email addresses or just one?

Customer: replied 9 months ago.
in that case it's not an email program - it's a php script sending confirmation emails to subscribing club members
i worked for years without any issues, but since 3 to 4 weeks emails to hotmail accounts fail.
Expert:  Josh replied 9 months ago.

To all Hotmail accounts?

Customer: replied 9 months ago.
it seems so
Expert:  Josh replied 9 months ago.

What is your domain?

Customer: replied 9 months ago.
domain is
Expert:  Josh replied 9 months ago.

Thank you. I wanted to check to see if your domain was blacklisted at all and it is not.

Was that the full error messages that you pasted above or was there more to it?

Customer: replied 9 months ago.
Content-Description: Delivery report
Content-Type: message/delivery-statusReporting-MTA: dns;
X-Postfix-Queue-ID: CEF2C80B8A
X-Postfix-Sender: rfc822;***@******.***
Arrival-Date: Sat, 22 Oct 2016 13:10:28 +0200 (CEST)Final-Recipient: rfc822;***@******.***
Action: failed
Status: 5.7.0
Remote-MTA: dns;
Diagnostic-Code: smtp; 550 5.7.0 (COL004-MC5F9) Message could not be delivered.
Please ensure the message is RFC 5322 compliant.--CEF2C80B8A.1477134631/
Content-Description: Undelivered Message
Content-Type: message/rfc822
Content-Transfer-Encoding: 8bitReturn-Path: <*****@******.***>
Received: by (Postfix, from userid 121)
id CEF2C80B8A; Sat, 22 Oct 2016 13:10:28 +0200 (CEST)
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00,
autolearn_force=no version=3.4.0
Received: from (idefix [])
by (Postfix) with ESMTP id A76B37F94D
for <*****@******.***>; Sat, 22 Oct 2016 13:10:28 +0200 (CEST)
Date: Sat, 22 Oct 2016 13:10:30 +0200
From: Webservice Kursanmeldung <>
Subject: =?UTF-8?Q?Anmeldung_Anf=C3=A4nger_Brust_(mit_Seepferdchen)_5-7_Jahre_mit_?=
Message-ID: <*****@******.***>
Customer: replied 9 months ago.
Are you still there?
Expert:  Josh replied 9 months ago.

Yes, I am.

Are you the person the "IT" person for the company that would fix email related issues?

Customer: replied 9 months ago.
That's me - yes
Expert:  Josh replied 9 months ago.

I will opt out of this question so that someone can review your PHP script that is being sent out. Something within that script is being rejected by Microsoft/Hotmail servers.

Expert:  Richard replied 9 months ago.

Hi there and welcome

If you look at the from address it is Webservice Kursanmeldung

Hotmail requires it to be an actual email address.

Update your script so it is an actual email address in the from field and tell me if it then sends correctly please.

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