Can't send an email from Outlook to hotmail.com address

Michelle Johnson 0 Reputation points
2026-11-06T21:31:07.2+00:00

I keep getting the following status code (550 5.7.23); what can I do to remedy the issue?

Outlook | Windows | New Outlook for Windows | For business

2 answers

Sort by: Most helpful
Most helpful Newest Oldest
  1. Chris-D 2,620 Reputation points Independent Advisor
    2026-11-06T21:58:41.64+00:00

    Hi Michelle,

    Thank you for sharing your concern.

    The error code 550 5.7.23 usually indicates that the receiving server rejected the message because it could not validate the sender’s domain. This is commonly caused by an incorrect or incomplete SPF record.

    If you are a Microsoft 365 administrator, you can try the steps below:

    1. Go to the DNS provider that hosts your domain’s DNS records and review the SPF TXT record.
    2. Make sure there is only one SPF record for the domain.
    3. If your organization sends email only through Microsoft 365, the SPF record should generally include: v=spf1 include:spf.protection.outlook.com -all
    4. If you also send email through an on-premises mail server or a third-party service, such as a CRM or bulk-mail platform, make sure those sending sources are included in the same SPF record.
    5. Confirm that the sending domain has been added and verified under Microsoft 365 admin center > Settings > Domains.
    6. Run a message trace in the Exchange admin center to check whether the message was blocked or routed through the High Risk Delivery Pool.

    Do not create multiple SPF records, as this can cause SPF validation to fail. Also, avoid replacing the existing record before confirming whether your organization uses any other email-sending services.

    For reference, you may find these articles helpful:

    Additionally, if needed, your IT team can also raise a support ticket with Microsoft Support through the Microsoft 365 Admin Center for deeper investigation. They have access to backend configurations and can perform a more in-depth investigation. At the very least, they can provide the most effective workaround to ensure your experience remains smooth and secure.      

    I hope this information is helpful. Should you have any further questions or need additional assistance, please feel free to share them in the comment below. I'm very happy to help.  

    If the answer is helpful, please click 'Yes' and kindly upvote it.

    Note: Please follow the steps in the forum documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

    Was this answer helpful?

    0 comments

  2. AI answer

    2026-11-06T21:32:17.3533333+00:00

    A Microsoft 365 email administrator must resolve 550 5.7.23; changing settings or reinstalling New Outlook will not correct this server-side delivery failure. ^1^

    If you are not the administrator

    Send your administrator:

    • The complete non-delivery report (NDR), including Diagnostic information for administrators.
    • The sender and recipient addresses, message time, and message subject.
    • This error-specific Microsoft guidance: 550 5.7.23 generally means the sending domain’s SPF record is missing or misconfigured. ^2^

    No Outlook client change is indicated by this code.

    Administrator remediation

    1. Inspect the original error in the NDR In Diagnostic information for administrators, identify the sending domain and the original rejection returned when Exchange Online attempted delivery.
    2. Confirm that the sending domain is provisioned Go to Microsoft 365 admin center → Settings → Domains. Confirm that the domain used by the sender is listed and healthy. Microsoft limits mail sent from unprovisioned domains. ^1^
    3. Check the domain’s SPF TXT record Query the public DNS record with an SPF/DNS checker. There must be only one SPF record for each domain or subdomain, and it must authorize every system that legitimately sends mail for that domain. SPF records are changed at the DNS hosting provider or domain registrar, not in a Microsoft 365 admin portal. ^3^ If standard commercial Microsoft 365 is the only sender, the documented value is: 
         v=spf1 include:spf.protection.outlook.com -all
      Do not replace an existing SPF record with that value if mail also originates from an on-premises server, bulk-mail platform, CRM, or another service. Add all legitimate sources to the single SPF record. Each sending subdomain needs its own record. GCC High, DoD, and Microsoft 365 operated by 21Vianet use different documented include values; do not use the commercial value for those environments. ^3^
    4. Include applicable on-premises senders If an on-premises mail system relays messages using this domain, add its public sending IP address or range to SPF. Also review any unprovisioned domains relayed through Microsoft 365. ^1^
    5. Check whether the message used the high-risk delivery pool Run Message trace in the Exchange admin center and inspect OutboundIpPoolName in the trace output. Messages classified as spam can be routed through the high-risk delivery pool; these messages do not pass SPF at the destination, and delivery is not guaranteed. ^4^
    6. Retest after DNS propagation Allow the DNS record’s configured TTL to expire, then send a new, plain message to the Hotmail recipient. Do not merely resend the original NDR item.

    Escalation

    If SPF is valid, the domain is provisioned, and message trace shows that the message was incorrectly classified as spam, open a Microsoft 365 support request. Microsoft specifically recommends contacting support for an incorrect outbound-spam determination. ^1^

    References

    1. Fix NDR error "550 5.7.23" in Exchange Online
    2. Troubleshoot email authentication in Microsoft 365
    3. Set up SPF to identify valid email sources for your custom cloud domains
    4. Outbound delivery pools
    AI-generated content may be incorrect. Read our transparency notes for more information.

    Was this answer helpful?

Your answer

Answers can be marked as 'Accepted' by the question author and 'Recommended' by moderators, which helps users know the answer solved the author's problem.