Hotmail emails are being returned as spam

Reinstalling or changing phone apps will not resolve a server-side 550 rejection; send one plain-text message from Outlook.com in a browser, then give Microsoft Support the complete 550 subcode and diagnostic text if it is also rejected.

Test the account directly

1. Sign in to Outlook.com in a web browser using the affected Hotmail account.
2. Create a new message to one trusted recipient.
3. Type the recipient’s complete address manually.
4. Remove the signature and send only plain text—no attachment, image, link, forwarding history, or repeated text.
5. Check the result:
   • If it sends: the original message content, signature, attachment, or recipient filtering is triggering the rejection. Add the content back gradually to identify it. Signatures and spam filters can affect delivery.^1^
   • If it still returns a 550 error: this is not an Android, Outlook-app, or Samsung-app installation problem. Continue below.

Record the complete error

Open the returned postmaster message and copy the section named Diagnostic information for administrators. The digits and text after 550 determine the next action; 550 by itself is not specific enough. Microsoft recommends using that diagnostic section to identify why delivery failed.^2^

Examples:

• 550 5.7.520 ... AS(4810), including failure of the plain-text browser test, can indicate an account-specific outbound restriction. Request an Outlook.com account review and supply the complete non-delivery report.^3^
• If only one recipient or one recipient domain rejects the message, ask that recipient to add the Hotmail address to their Safe senders list. Their mail provider may be applying the block.^4^
• If the bounce says relay denied, mailbox full, invalid recipient, or names a different code, follow that exact reason rather than treating it as an account spam restriction.

Check account security

A restriction can follow suspicious sending activity, but the error alone does not prove the account was compromised.

1. Review the Microsoft account’s Recent activity for unfamiliar sign-ins, devices, or applications.
2. For an unfamiliar entry, select This wasn’t me or Secure your account.
3. Change the password and update security information if anything is suspicious. The activity page shows significant account access from the last 30 days.^5^
4. Review Sent Items for messages you did not send.

Request Microsoft’s account review

If the plain-text browser message is rejected:

1. While signed in to the affected Hotmail account, open Outlook.com.
2. Select Help on the menu bar and enter the full error, for example:
   Personal Hotmail account cannot send from Outlook.com or mobile; plain-text test fails with 550 [full code].
3. If self-help does not resolve it, scroll to Still need help?, select Yes, and request support.
4. Include:
   • The complete 550 code and accompanying text.
   • The Diagnostic information for administrators section.
   • Whether every recipient or only certain domains are affected.
   • Confirmation that a plain-text message from Outlook.com in a browser also failed.

This is the supported Outlook.com escalation route for persistent sending failures.^1^ Do not post the email address or full message headers publicly. A new email address should not be necessary merely to request review of the existing account.

References

1. Can't send or receive email in Outlook.com | Microsoft Support
2. Failed delivery messages from the postmaster at outlook.com, microsoft.com, or service.microsoft.com
3. I can receive emails but cannot send. Error 550 5.7.520 AS(4810) - Microsoft Q&A
4. Sender Support in Outlook.com | Microsoft Support
5. Check the recent sign-in activity for your Microsoft account