I cannot send emails

The 550 5.7.520 … identified as spam. AS(4810) response means Outlook.com’s spam filter is blocking the outgoing message, so send a brand-new plain-text message with no signature or quoted conversation to determine whether specific content is triggering it.

Send a clean plain-text test

Since different recipients, storage, browsers, attachments, links, and account security have already been checked, do not repeat those steps.

1. In Outlook.com, select Settings (gear icon) → Mail → Compose and reply.
2. Change the message format from HTML to Plain text.
3. Temporarily remove your automatic signature from the same settings page. Microsoft notes that signatures can sometimes prevent messages from sending.^1^
4. Select New mail—do not reply to or forward an existing conversation.
5. Send one recipient a short message such as:

   Test message. Please confirm receipt.

   Do not add a signature, pasted formatting, images, links, attachments, repeated text, or previous conversation history.

This exact error has been resolved in similar Outlook.com cases by removing the signature and switching to plain text.^2^

• If the test sends: Add the subject, signature, formatting, and other content back one element at a time. The element after which delivery fails is triggering the filter. Keep it removed or rewrite it.
• If the clean test also fails: The block is no longer isolatable to ordinary message content and needs review by Outlook.com Support.

Escalate a persistent block

In Outlook.com:

1. Select Help on the menu bar.
2. Enter: 550 5.7.520 AS(4810) all outgoing messages blocked.
3. Complete the suggested self-help.
4. Scroll to Still need help?
5. Select Yes, then Contact Support.^1^

Include:

• The complete error code: 554 5.7.0 / 550 5.7.520 / AS(4810).
• That it happens with different recipients and domains.
• That a new, plain-text, signature-free message with no links or attachments also fails.
• The approximate date and time of the latest failed test, including your time zone.
• The generating server shown in the delivery report.

Remove email addresses and other personal information from screenshots or copied diagnostics. Outlook.com’s documented support path is the appropriate escalation when normal sending checks do not resolve a non-delivery report.^3^

Do not use domain-authentication, SMTP-server, or blocklist-removal procedures intended for organizations that operate their own domain or mail server; this is a personal Hotmail/Outlook.com mailbox.

References

1. Can't send or receive email in Outlook.com | Microsoft Support
2. I can’t send emails. All are marked as spam - Microsoft Q&A
3. Fixes or workarounds for recent issues on Outlook.com | Microsoft Support