Mailybox
check dmarcdiagnose a bounce
Home / Email errors / outlook
outlook error

Outlook.com 550 OU-001 / OU-002 — Content Rejected

Outlook.com rejected the message on content grounds: the message or the links inside it matched patterns Microsoft associates with spam or phishing.

Diagnose your exact bounce Email Infrastructure Digital Twin

What the bounce says

Exact wording as it appears in the rejection or NDR. Placeholders such as x.x.x.x and example.com stand for your own address and domain.

550 OU-001 Mail rejected by Outlook.com for policy reasons. If you are not an email/network admin please contact your Email/Internet Service Provider for help.

550 OU-002 Mail rejected by Outlook.com for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation.

OU codes are content-based. Microsoft found something in the message — links, structure, wording — that resembles known spam or phishing, and rejected it regardless of the sender’s reputation. The fix is in the message, not in DNS.

Reviewed 2026-09-08. Provider wording and requirements change; the provider reference below is authoritative.

Most common causes

  • URLs in the message point at domains with poor reputation
  • Content resembles phishing or scam templates
  • Link shorteners or tracking domains with bad history
  • Obfuscated text or hidden content

What to verify next

  1. Review every domain linked in the message, including tracking and image hosts
  2. Remove shorteners and use your own tracking domain
  3. Simplify the template and avoid patterns common in scams
  4. Request review through sender support after cleaning the content

What is judged

Every URL in the message is checked against reputation data, including image hosts, tracking domains and link shorteners. Templates that resemble common scams — payment requests, account alerts, prize notices — score badly even when legitimate. Hidden text, tiny fonts and image-only bodies add to the score.

A single bad link is enough; the rest of the message does not compensate.

  • Every linked domain is scored.
  • Scam-like templates are penalized.
  • Hidden or image-only content counts against the message.

Clean the message

List every domain referenced in the HTML and check each on public reputation services. Replace shorteners with direct links on your own domain. Use a tracking domain you control. Simplify the template and make the text match the purpose plainly.

Test before resending

Send the cleaned message to a test Outlook.com mailbox before the campaign. If it is accepted, roll out; if rejected again, remove links one at a time to find the offender.

Best diagnostic path

Live analysis

Mail Failure Doctor

Classify the complete rejection and preserve provider-specific diagnostic context.

Open analysis → Live analysis

Email Infrastructure Digital Twin

Map the domain’s public mail infrastructure and provider relationships before remediation.

Open analysis →

Known limits

  • Microsoft does not say which element triggered the block.
  • Link reputation changes over time; a clean domain can become listed.

Common questions

Our domain is fine. Why blocked?

A third-party domain in the message — a tracking host, an image CDN, a shortener — is the usual cause.

Difference between OU-001 and OU-002?

OU-002 explicitly mentions content with spam-like characteristics or reputation; OU-001 is the general form. Treat both as content problems.

Does plain text help?

Often. A plain-text version with direct links is the fastest way to test whether the HTML is the problem.

Why the exact message matters

The same status family can be triggered by different conditions, and providers frequently add diagnostic text that narrows the issue. Use the complete rejection text rather than treating the numeric code as a complete diagnosis.

Provider reference

For the provider-defined meaning and current requirements, review Microsoft Outlook.com sender troubleshooting.