My sent emails are all being bounced back as spam

Question

My sent emails are all being bounced back as spam

Brenan Properties 0

It's a newish email address I've set up as a point of contact for gathering certain information for a small group of people (tenants). Everytime I try to send an email to them i'm getting the following

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)>'

How does this unblock? I'm not sending spam, I'm sending a relatively similar email to the people to outlining 3-4 bits of information I need from them.

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ic 0 Reputation points

2026-10-22T01:18:37.83+00:00

Hi @Alice-N , I am facing the same issues. I have tried the steps you outlined, but am still receiving the same issue whenever i tried to email external parties.
Hornblower409 18,700 Reputation points

2026-10-23T19:34:03.36+00:00

@ic said

I am facing the same issues. I have tried the steps you outlined, but am still receiving the same issue whenever i tried to email external parties.

I understand that you have the same or similar issue to the one discussed in this thread. But you will probably not get any help by adding to an old post.

I would suggest that you start a new thread using the "Ask a question" button at the top of this page to create a new Question and include the details for your specific problem and what steps you have already tried to fix it.

This provides much higher visibility to your issue than adding on to an existing post, which is only seen by people who are already following this question.

2 answers

ic 0 Reputation points

2026-10-22T01:18:37.83+00:00

Hi @Alice-N , I am facing the same issues. I have tried the steps you outlined, but am still receiving the same issue whenever i tried to email external parties.
Hornblower409 18,700 Reputation points

2026-10-23T19:34:03.36+00:00

@ic said

I am facing the same issues. I have tried the steps you outlined, but am still receiving the same issue whenever i tried to email external parties.

I understand that you have the same or similar issue to the one discussed in this thread. But you will probably not get any help by adding to an old post.

I would suggest that you start a new thread using the "Ask a question" button at the top of this page to create a new Question and include the details for your specific problem and what steps you have already tried to fix it.

This provides much higher visibility to your issue than adding on to an existing post, which is only seen by people who are already following this question.

Answer 1

Hi Brenan Properties

I understand you’re having an issue where outgoing messages are being rejected with:

550 5.7.520 Message blocked because it contains content identified as spam. AS(4810). Are the recipients using Microsoft mailboxes (Outlook.com/Hotmail/Microsoft 365), and does the bounce come from ******@outlook.com?

Please follow these steps if the AI steps do not work:

1) Confirm the bounce is legitimate and capture the exact diagnostic details

Open the non‑delivery report (NDR) and scroll to “Diagnostic information for administrators” to confirm the precise reason and any additional details. Verify if the message is genuinely from ******@outlook.com / [email protected] / service.microsoft.com and not spoofed.

2) Try sender reputation steps

If you run anti‑virus software, temporarily disable any feature named “Internet Email Auto Protect” or “Internet Email Protection”, then send a test email again.
Add a clear display name to your outgoing email so the “send as” identity is easily recognizable.
Send an email to yourself, open it, and reply to it.
Add frequent recipients to your Contacts list. Using Contacts as part of reputation improvement.
Ask recipients to add your address to their Safe senders list.
Avoid sending to too many people at once (reduce volume/frequency if you suspect throttling/reputation impact).
See: https://support.microsoft.com/en-us/office/sender-support-in-outlook-com-05875e8d-1950-4d89-a5c3-adc355d0d652

3) Check Outlook.com sending limits (especially for new accounts)

If this Outlook.com address is newly created, it may have a temporary low sending quota until credibility is established. See: Sending limits in Outlook.com - Microsoft Support

Please tell me how it goes. If the problem persists, please don’t hesitate to reply to this thread and I will be happy to help. Have a lovely day!

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

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Alice-N 13,405 Reputation points Microsoft External Staff Moderator

2026-04-19T00:48:47.3666667+00:00

Hi Brenan Properties

I hope you are doing well ! I just want to check if you have had a chance to check my reply earlier? Please let me know.

Have a lovely day!

Answer 2

The error means Outlook.com’s spam filters are classifying the messages as spam based on content, sending pattern, or reputation, even if the messages are legitimate.

To improve deliverability and get unblocked:

Vary and simplify the message content
- Avoid sending many nearly identical messages in a short time.
- Change subject lines slightly and personalize the body (names, specific details) so they are not all the same template.
- Remove or reduce:
  - Excessive links
  - Spam‑like phrases (urgent payment, prizes, etc.)
  - Large attachments
Check that the account is not compromised
- Review Sent Items, Deleted Items, and Inbox rules for anything suspicious (unexpected forwarding rules, auto‑delete rules, etc.), as these can cause reputation issues that trigger blocking.
- If anything suspicious is found, follow guidance to respond to a compromised account and secure it (change password, remove malicious rules, etc.).
Improve sender reputation and behavior
- Send to people who expect the messages and are likely to read them.
- Ask recipients to:
  - Add the address to their safe senders list.
  - Mark any misclassified messages as “Not junk” in their mailbox.
- Avoid sending to invalid or non‑existent addresses repeatedly.
Use Outlook.com sender support if needed
- If messages still get blocked after adjusting content and behavior, use the Outlook.com sender support troubleshooting form (for Outlook.com system deliverability issues) to request help analyzing and improving the sender reputation.

These steps help align with Microsoft’s anti‑spam protections so legitimate bulk or similar messages are less likely to be blocked.

References: