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Email Delivery Failure from Exchange Online to Gmail - 550 5.7.1 Low Reputation Error

Vladyslav 0 Reputation points
2025-12-09T14:15:03.5+00:00 
We are unable to deliver emails from our Microsoft 365 (Exchange Online) domain to Gmail recipients. Emails are rejected by Gmail with the following NDR (Non-Delivery Report) error:

"550-5.7.1 [ts11-2002-003] Our system has detected that this message is likely spam, and it has been rejected. The reason for the rejection is: very low reputation. Please visit https://support.google.com/mail/?p=LowReputation to diagnose and fix the issue. While you have been sending mail with low reputation, we have detected that this message is likely spam and it has been rejected. Please visit https://support.google.com/mail/?p=LowReputation to diagnose and fix the issue. PC Order: 11573-SMTP0172-6732"

This issue started on [date, e.g., November 12, 2025] and affects all outbound emails to @gmail.com addresses. It is severely impacting our business communications (e.g., customer support, invoices).

**Troubleshooting steps we've taken:**
- DNS authentication verified: SPF record includes "include:spf.protection.outlook.com" (passes MX Toolbox check), DKIM enabled and verified (selector: [your selector, e.g., selector1._domainkey]), DMARC policy set to quarantine (p=quarantine; rua=mailto:******@yourdomain.com).
- No bulk or high-volume sending; emails are legitimate business/transactional (low volume, no suspicious content/attachments).
- Checked Exchange Online Message Trace: Messages are sent successfully from our side, but bounced by Gmail. No policy violations, malware, or spam filters triggered in M365.
- Domain registered in Google Postmaster Tools: Shows low spam complaint rate (under 0.1%), but overall reputation flagged as low.
- IP range: Using Microsoft 365 outbound IPs (e.g., 40.92.0.0/13) – not listed in major DNSBLs (verified via Talos Intelligence).
- Submitted delisting request to Google (via support.google.com/mail/contact/delisted), but awaiting response.

Request:
Please investigate this on Microsoft's end: Confirm if our tenant/IP has any reputation issues with Google, check for any outbound connector problems, or escalate to Google for whitelist review. We need urgent resolution as this blocks ~[X]% of our external emails.

Details:
- Affected domain: akvantis.com.ua
- Bounce ID: PC Order 11573-SMTP0172-6732
- Attached: Screenshots of bounce message, DNS verification results, and Message Trace log.

Priority: High – Business-critical.

Thank you for your assistance.
Exchange | Exchange Server | Other
Exchange | Exchange Server | Other
A robust email, calendaring, and collaboration platform developed by Microsoft, designed for enterprise-level communication and data management.Miscellaneous topics that do not fit into specific categories.
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  1. Q&A Assist
    2025-12-09T14:15:21.7866667+00:00
    AI generated content. This question contains an answer created with AI from Q&A Assist. Learn more

    The error message you are encountering, "550-5.7.1... very low reputation," indicates that Gmail is rejecting your emails due to a low reputation associated with your sending domain or IP address. Here are some steps to consider for troubleshooting and potentially resolving this issue:

    1. SPF, DKIM, and DMARC Configuration: Ensure that your SPF record is correctly set up and includes all necessary sources. Since you mentioned that your SPF record includes include:spf.protection.outlook.com, ensure that it is correctly configured and passes checks. Additionally, verify that DKIM is properly set up and that your DMARC policy is appropriate for your needs.
    2. Monitor Sending Behavior: Since you are not sending bulk emails and your emails are legitimate, continue to monitor your sending patterns. Avoid any practices that could be perceived as spammy, such as sending emails to unengaged recipients or using misleading subject lines.
    3. Google Postmaster Tools: Since you have registered your domain in Google Postmaster Tools and noted a low spam complaint rate, continue to monitor your reputation there. The overall reputation being flagged as low suggests that there may still be issues with how Gmail perceives your sending behavior.
    4. IP Reputation: Although you have verified that your IPs are not listed in major DNSBLs, consider checking your sending IP against reputation monitoring services to see if there are any issues that may not be reflected in the DNSBLs.
    5. Delisting Request: You mentioned that you submitted a delisting request to Google. Ensure that you provide all relevant information and be patient, as responses can take time.
    6. Contact Microsoft Support: Since you are using Microsoft 365, consider reaching out to Microsoft support for further assistance. They may be able to provide insights into your tenant's reputation and whether there are any outbound connector issues that need addressing.
    7. Escalate with Google: If the issue persists, you may need to escalate your case with Google, especially if your business communications are critically affected. Providing them with detailed information about your sending practices and the steps you have taken may help in getting a resolution.

    By following these steps, you can work towards improving your email reputation and resolving the delivery issues to Gmail recipients.

    References:

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  2. Andy David - MVP 159.7K Reputation points MVP Volunteer Moderator
    2025-12-09T17:28:25.77+00:00

    No one here can investigate this. You should open a ticket with 365 support if that is needed.

    I will note that your domain does not have an enabled DMARC policy. None is effectively the same as not having one. I would set the policy to "reject" and see if that makes things better.

    https://v4.hkg1.meaqua.org/en-us/defender-office-365/email-authentication-dmarc-configure

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