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Outlook | Windows | New Outlook for Windows | For home
Using New Outlook on Windows for personal email, calendar, and contact management
The error 550 5.7.520 Message blocked because it contains content identified as spam. AS(4810) means the Outlook/Hotmail/MSN filtering system has classified the specific message as spam and blocked it, even though it is being sent to the same personal account.
Key points about what is happening:
- The message is being rejected by the recipient’s email provider (Microsoft consumer mail – Outlook.com/MSN/Hotmail).
- The spam filter is acting on the content and/or format of the message, not on the fact that it is self‑to‑self.
- This is a server‑side decision; the message never reaches the inbox.
Practical steps to resolve or work around it based on the Outlook.com delivery‑failure guidance:
- Check the message content and format
- Avoid very short or meaningless subjects/bodies (for example, just
vvv). - Remove suspicious wording, large numbers of links, or anything that looks like bulk/unsolicited mail.
- In the sample headers, the message is sent as
application/ms-tnef(winmail.dat). Try sending as plain text or standard HTML instead of rich‑text/TNEF.
- Avoid very short or meaningless subjects/bodies (for example, just
- Resend after a short time
For transient blocks and filtering decisions, Microsoft guidance for similar delivery failures is to wait a short time and resend. Some errors “fix themselves over time” as filters update. - Verify the address and mailbox status
Even though this is the same personal address, the standard checks still apply:- Ensure the address is correct and active.
- Make sure the mailbox is not full (quota exceeded) and is not otherwise unavailable.
- If the problem persists, adjust how the account is used
- Avoid sending many near‑identical test messages or bulk mail to the same account, which can train filters to treat the traffic as spam.
- If sending from a different service/domain into the MSN/Outlook.com account, ensure that service is not on a blocklist and that its messages are not generally being treated as spam.
If messages to other recipients work but messages to the MSN/Outlook.com address consistently bounce with spam‑related codes, the issue is with how the receiving Microsoft consumer service is classifying those specific messages, and changing content/format and resending is the supported path.
References: