emails rejected at gmail because of failed DMARC verification

Dr. Sebastian Dunda 0 Reputation points
2026-01-12T12:01:26.5933333+00:00

Unfortunately, since 4 days, all of emails send to gmail- or outlook-account are rejected because they did not pass DMARC verification as followed:

[<Moderator note: personal info removed> .mail.protection.outlook.com] rejected your message to the following email addresses:

[<Moderator note: personal info removed>@hotmail.de (<Moderator note: personal info removed>@hotmail.de)] Your message wasn't delivered because the recipient's email provider rejected it.

[<Moderator note: personal info removed>.mail.protection.outlook.com] gave this error: Access denied, sending domain [<Moderator note: personal info removed>] does not pass DMARC verification and has a DMARC policy of reject. [<Moderator note: personal info removed>.PROD.OUTLOOK.COM] 2026-01-12T11:40:05.302Z <Moderator note: personal info removed>] [<Moderator note: personal info removed>.PROD.OUTLOOK.COM] 2026-01-12T11:40:04.078Z <Moderator note: personal info removed>] [<Moderator note: personal info removed>.prod.outlook.com] 2026-01-12T11:40:05.321Z 08DE4EBCD5BA18F0]

Diagnostic information for administrators:

Generating server: [<Moderator note: personal info removed>.PROD.OUTLOOK.COM]

[<Moderator note: personal info removed>@hotmail.de] [<Moderator note: personal info removed>.mail.protection.outlook.com] Remote server returned '550 5.7.509 Access denied, sending domain [<Moderator note: personal info removed>] does not pass DMARC verification and has a DMARC policy of reject. [<Moderator note: personal info removed>.PROD.OUTLOOK.COM] 2026-01-12T11:40:05.302Z <Moderator note: personal info removed>] [<Moderator note: personal info removed>.PROD.OUTLOOK.COM] 2026-01-12T11:40:04.078Z <Moderator note: personal info removed>] [<Moderator note: personal info removed>.prod.outlook.com] 2026-01-12T11:40:05.321Z <Moderator note: personal info removed>]'

Original message headers:

ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=
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  1. AI answer

    2026-01-12T12:01:36.6133333+00:00

    The issue you are experiencing with emails being rejected by Gmail and Outlook due to DMARC verification failures is likely related to the DMARC policy set for your domain, SEBASTIAN-DUNDA.DE. Since your DMARC policy is set to p=reject, any emails that fail DMARC checks will be rejected by the recipient's email provider.

    To resolve this issue, you should check the following:

    1. SPF and DKIM Records: Ensure that your SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) records are correctly configured. These records help authenticate your emails and are crucial for passing DMARC checks.
    2. Alignment: Make sure that the domains used in the MAIL FROM and From headers are aligned. DMARC requires that these domains match or be part of the same organizational domain.
    3. DMARC Reports: Review your DMARC aggregate reports to identify any unauthorized sources sending emails on behalf of your domain. This can help you understand why your emails are failing DMARC checks.
    4. Testing: If you are in the process of configuring DMARC, consider temporarily changing the policy to p=none to allow for monitoring without rejecting emails. Once you have confirmed that your SPF and DKIM records are correctly set up, you can switch back to p=reject.

    By ensuring proper configuration and alignment of your email authentication records, you should be able to resolve the DMARC verification failures and prevent your emails from being rejected.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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  2. Hin-V 16,830 Reputation points Microsoft External Staff Moderator
    2026-01-12T14:05:07.1+00:00

    Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data. 

    Hi @Dr. Sebastian Dunda

    Thank you for posting your question in Microsoft Q&A. 

    I understand that you are experiencing an issue when sending emails from your business account. The message you are receiving: “550 5.7.509 Access denied, sending domain <your domain> does not pass DMARC verification and has a DMARC policy of reject.” indicates that this issue is related to your domain’s DMARC configuration. Specifically, emails sent from your domain are failing DMARC authentication, and because the DMARC policy is set to reject, the recipient mail server is refusing the messages. 

    To help us investigate further, could you provide additional information for the following questions: 

    Did this issue start after any recent changes (for example, mail server changes, DNS updates, or enabling DMARC)? 

    Does this behavior affect all users in your tenant or only specific mailboxes? 

    In the meantime, I recommend contacting your IT administrator or domain administrator to review the SPF, DKIM, and DMARC records for your sending domain and ensure they are configured correctly. 

    For additional guidance, you could refer to the following Microsoft documentation: Use DMARC to validate emails and setup steps - Microsoft Defender for Off... 

    Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution. 

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

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