Emails not sending, POST MASTER?

Question

Emails not sending, POST MASTER?

James Graham 0

Getting this error

Tried using Web page & IOS Phone to narrow down issue to the account.

Remote server returned '554 5.7.0 < #5.7.520 smtp;550 5.7.520 Message blocked because it contains content identified as spam. AS(4810)>'

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3 answers

Your answer

Answer 1

SD - IA 181.1K Independent Advisor

Hi,

As I said, the steps must be done on Outlook for web, for iOS it will not work.

How many emails do you send per day?

0 comments

Answer 2

Hi,

Because of spam abuse, Microsoft has placed restrictions and imposed a daily email limit, especially for recently created accounts.

550 5.7.520 Message Blocked Error in Outlook (4810): How to Fix It
https://yourwindowsguide.com/2026/09/550-5-7-520-message-blocked-error.html

Sending limits in Outlook.com
https://support.microsoft.com/outlook/sending-limits-in-outlook-com

Also,

Do you have a signature in your Email? If so, please remove it temporarily and verify.

Second, try switching the Email to Plain Text instead of HTML as a troubleshooting step, on Web Outlook.

The setting is below:

Open The Gear icon > Settings.
Go to Mail > Compose and Reply.
Change the message format to Plain text.

If nothing works, file the form at https://sender.office.com and the restrictions will be lifted.

A friendly reminder that this is a user-to-user forum where users help other users.

Experts or Advisors participating here cannot make changes to Microsoft services or access internal systems and can only provide technical guidance, irrespective of Microsoft's Policy decisions.

I hope this information helps. If you have any more questions, don't hesitate to reach out. Wishing you good luck!

James Graham 0 Reputation points

2026-10-13T02:23:14.2366667+00:00

I don’t find the setting. All I need everything in my inbox not the spam please fix to help me out

Answer 3

The error means the message is being blocked as spam by the mail system, not that sending is generally unavailable. Since it happens from both Outlook on the web and an iPhone, the issue is likely with the account or message content rather than the device.

Try these steps:

Send a very simple test message to a single recipient.
- Use plain text only.
- Remove all links.
- Remove any signature.
- Do not attach files.
If that works, add content back gradually.
- First add normal body text.
- Then add the signature.
- Then add links or attachments one at a time. This helps identify what is triggering the spam block.
If sending to a group, reduce the recipient count and test with one person first. Group-style messages are more likely to be flagged.
If composing in Outlook on the web, switch the message format to plain text as a troubleshooting step.
- Open Settings
- Go to Mail > Compose and Reply
- Change the message format to Plain text
If a postmaster message is returned, review the diagnostic section in that message. Look for a section such as Diagnostic information for administrators. It usually contains the reason the message was rejected.
If the message includes a large attachment, reduce it. Messages with attachments larger than 10 MB can fail delivery. Save the file to OneDrive and share a link instead.

A legitimate message from ******@outlook.com, [email protected], or service.microsoft.com usually means the message could not be delivered to one or more recipients.