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Hotmail/ Outlook is rejecting Yahoo Mail,

d jak 10 Reputation points
2026-05-17T03:07:26.2166667+00:00

Started 5/12 , forward a email from yahoo to Outlook and get a mailer error, REJECTED BY HOTMAIL. Why is Outlook rejecting Yahoo Mail?

Outlook | Web | Outlook.com | Email
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  1. EmilyS726 233.2K Reputation points Independent Advisor
    2026-05-17T03:44:06.9666667+00:00

    Hello

    I think there's something going on Microsoft's end right now. I am seeing many people reporting that they cannot receive emails from Yahoo or Gmail users. You are not the only one. Earlier this week it happened with iCloud users, but it finally recovered. Hopefully this is a similar situation. There's no official announcement on Microsoft side at the moment.

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  2. AI answer

    2026-05-17T03:07:36.2333333+00:00

    Outlook.com/Hotmail rejects messages when the sending server or domain does not meet Microsoft’s current authentication and anti‑spam requirements.

    Two common causes from the provided information:

    1. Relay / unauthorized‑sender style failures (550/553)
      If the Yahoo message is being forwarded through another SMTP server (for example, an intermediate service or a misconfigured client), Outlook.com may see that server as not authorized to send for the Yahoo address and reject it with a 550/553 or “relaying denied” type error. In these cases, the Outlook.com SMTP server does not recognize the sender as an authorized user and refuses to relay or accept the message.
    2. Authentication requirements for high‑volume senders (550 5.7.515)
      If the Yahoo message is coming from a domain or service that sends large volumes of mail into Outlook.com and that domain does not meet Microsoft’s required authentication level (SPF/DKIM/DMARC alignment, etc.), Outlook.com can return an NDR like: “550 5.7.515 Access denied, sending domain <domain> does not meet the required authentication level. The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender.” In this case, Outlook.com is enforcing stricter authentication rules to reduce spam and phishing.

    What to do next depends on who controls the sending system:

    • If using automatic forwarding from Yahoo or another service into Outlook.com, review that service’s forwarding configuration so that messages are sent in a way that preserves proper authentication (SPF/DKIM/DMARC) for the original From domain.
    • If the error text includes 550 5.7.515, the owner of the sending domain (for example, an email service or IT admin) must update the domain’s email authentication to meet Microsoft’s requirements for high‑volume senders, as described in the non‑delivery report.

    References:

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