Frequent Contributor

I use my HP Chromebook x360 laptop to do MOST of my work- which ALWAYS consists of replying to emails.


Since Tuesday (July 5, 2022), my emails are not being sent and coming back as: "Delivery has failed to these recipients or groups: and Your message wasn't delivered because the recipient's email provider rejected it." And underneath, it reads: "Remote Server returned '550 5.7.520 Message blocked because it contains content identified as spam. AS(4810)' " 


I've tried 11+ different times to three separate email addresses (including to myself), but can not send, reply, OR even forward any of them. Yet, I can send, reply to, and forward messages from my "moto g stylus 5G," and yes- even to myself.


Here is a "copy" of the "returned message" from "Microsoft Outlook <email address removed for privacy reasons>" :



Delivery has failed to these recipients or groups:

email address removed for privacy reasons (email address removed for privacy reasons)
Your message wa...





Diagnostic information for administrators:

Generating server:

email address removed for privacy reasons
Remote Server returned '550 5.7.520 Message blocked because it contains content identified as spam. AS(4810)'

Original message headers:

Received: from (2603:10b6:907:e::33)
 by (2603:10b6:208:166::12) with
 Microsoft SMTP Server (version=TLS1_2,
 cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5395.17; Thu, 7 Jul
 2022 16:02:54 +0000
Received: from
 ([fe80::9e9:2087:471c:dd52]) by
 ([fe80::9e9:2087:471c:dd52%6]) with mapi id 15.20.5395.021; Thu, 7 Jul 2022
 16:02:54 +0000
Content-Type: application/ms-tnef; name="winmail.dat"
Content-Transfer-Encoding: binary
From: Rae Rae <email address removed for privacy reasons>
To: "email address removed for privacy reasons" <email address removed for privacy reasons>
Thread-Index: AQHYkhsEaJ30JmQlY0eOUDlxd7p+hQ==
X-MS-Exchange-MessageSentRepresentingType: 1
Date: Thu, 7 Jul 2022 16:02:54 +0000
Message-ID: <email address removed for privacy reasons>
Accept-Language: en-US
Content-Language: en-US
X-MS-TNEF-Correlator: <email address removed for privacy reasons>
MIME-Version: 1.0
X-TMN: [yQ+GA5RXWdia6nUwY1H3riqJGpQVUZjQf5XKjHsX2ig7rzTU7B9Az7MYe2YG6Jnc+9SM8nDUFJo=]
X-MS-PublicTrafficType: Email
Return-Path: email address removed for privacy reasons
X-MS-Office365-Filtering-Correlation-Id: 679a204a-aec0-48a4-a756-08da603226d3
X-MS-TrafficTypeDiagnostic: MN2PR07MB6720:EE_
X-Microsoft-Antispam: BCL:0;
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1


WHERE did I go wrong? And HOW do I (CAN I???) fix "this?" PLEASE.




15 Replies


550 5.7.520 Access denied, when forwarding to another org email - Microsoft Community

Hi this information should be helpful if it concerns work, and if it is a private (personal address) then the repair must be done by the account owner.



First, thank you for responding. I believe the "problem" began when I associated (my) Gmail w/ my Outlook- and vice-versa. Because now, I am getting the SAME emails sent to both addresses simultaneously. And, for the life of me, I can not remember HOW I did "that!" Is this something you can help me with, please?

Oh, FTR- "It" is a "personal address," and I AM the "account owner."


This is complicated because the recipients marked your messages as SPAM and now you are a blocked sender and blacklisted.
The combination of Gmail and Outlook is unlikely to matter because you can receive mail, but you can not send anything - write if I understand correctly?

550 5.7.520 Message blocked because it contains content identified as - Microsoft Community

Sender Support in (

Fix email sync issues (

Yes, you are correct- ONLY w/ Outlook on my laptop. However, I am COMPLETELY able to send emails (from Outlook) using my phone.
OMG! "This" is the message I get: "Step 1: Invalid email address or IP address. Please provide your email address and the IP address you want to delist so that verification can proceed." IDK what to do! Nothing seems to be helping- other than you (Andrzej1). Thank you for all you've done/ are doing.
ask your friends -> who can verify the information you need to help you fill the formula it is complicated so only so you can fix it
Could I have done "this" to myself? What I mean is, there have been a couple of times where I found an email (in my junk folder, while on my laptop) that reads it is "from" (my FULL name), but I NEVER sent anything to myself, so I marked it as spam. Could "this" be why I can not send from my laptop but CAN when using the app on my cell phone?


Yes it's your mistake, even if you found yourself as spam you have to mark on another device, e.g. phone (add to safe senders)


Select SettingsSettings> View all Outlook settings.

Select Mail, and then select Junk email.

A screenshot shows the Junk email window in the Mail area of Settings.

If you see the sender's address listed under Blocked senders and domains, select their address and then select Remove Remove > Save.

If the sender's address isn't in your Blocked senders list, you can add them to Safe senders and domains. Email from contacts in your safe senders list will never go to the Junk Email folder.

Select SettingsSettings> View all Outlook settings.

Select Mail, and then select Junk email.

A screenshot shows the Safe senders area of the Junk Email settings in Mail in Settings for

Enter the sender's email address, and then select Add > Save"

If you are getting sent to one address in two mailboxes, either the outlook mailbox is forwarding to Gmail or Gmail is configured to go out and get mail.

In each account, check settings - in outlook on the web, its's Settings (gear icon) > View all Outlook settings > Mail - Rules and Forwarding. In Gmail its under the POP/IMAP/forwarding section in Settings.

As for the spam - your messages are being converted to RTF format. That can cause some filters to reject it.
>> Content-Type: application/ms-tnef; name="winmail.dat"
Are you using Outlook desktop or Outlook on the web to send?

When addressing mail, when the address comes up in the autocomplete list, delete it then select it from contacts.

Note: delisting is for your mail server IP - if you are using, you cannot delist it.

Hi @Diane Poremsky 

Can you explain what settings in Outlook led to such outgoing mail blocking?

" And underneath, it reads: "Remote Server returned '550 5.7.520 Message blocked because it contains content identified as spam. AS(4810)' " "

Best guess: messages with winmail.dat files are being identified as spam, possibly because its a .dat file. It could be because the filters can't scan the winmail.dat file and it may contain an infected attachment.

If you are using HTML message format and send a meeting invite in outlook format, the autocomplete entry for the address is updated to use RTF. All future messages may be sent RTF until you delete the autocomplete entry.

If using Outlook desktop, you can set a registry key to prevent using RTF.

@Diane Poremsky 

Thank you
I understand, but why the user after many years, suddenly without changing the settings, is blocked?
Plain text (not HTML) won't do that.
However, I guess that this was caused (reports - spam) by other users -> this is a big problem for the sender of the mail!'

I am using Outlook on the web (
best response confirmed by Rae_Rae (Frequent Contributor)
Update(?): I read somewhere there is an update in progress, which will go through July 15, 2022. I will have to wait until after that date and check again. MEANTIME, though, I (LUCKILY) have another source to send, reply to, and forward(?) messages. Inconvenient, but at least "it" is there!