Urgent: Sudden Block Bounces to Outlook/Hotmail Domains - email.israelbonds.com

Question

Dear Microsoft Postmaster Team,

We are experiencing a sudden and severe deliverability issue to Microsoft domains (Outlook.com, Hotmail.com, Live.com, MSN.com) that began on January 28, 2026.

 ISSUE DETAILS:

• Sending Domain: email.israelbonds.com
• Issue Start Date: January 28, 2026
• Affected Volume: ~5,700-6,200 block bounces per send (99% of all Microsoft recipients)
• Previous Performance: <0.5% bounce rate (normal)

WHAT WE'VE VERIFIED:

SPF, DKIM, DMARC all passing authentication

• No changes to sending infrastructure or volume
• No changes to content or send frequency
• Other ISPs (Gmail, Yahoo) delivering normally

 

ERROR MESSAGES RECEIVED:

550 Blocked

SENDING HISTORY:

• Weekly volume: ~112,000 emails
• Complaint rate: less than 0.01% over the last year 
• List composition: Opted-in subscribers, no purchased lists
• ESP: Salesforce Marketing Cloud

REQUEST:

We suspect this may be related to a recent policy change or filtering adjustment on Microsoft's end, as:

1. The issue started suddenly with no changes on our side
2. It affects 99% of Microsoft recipients uniformly
3. Our authentication is passing
4. We have a clean sending history

 

Could you please:

1. Investigate if our domain is on an internal blocklist
2. Check if there was a filtering policy change affecting our sends
3. Advise on any steps needed to resolve this issue

We are prepared to provide additional information or work with your team to resolve this quickly.

 

Thank you for your assistance.

John Hercel

Associate Marketing Director

Marketing & Communications

<removed PII>

Answer 1

Hello,

You would need to use Microsoft's SNDS portal to request further review and get sender support.

https://sendersupport.olc.protection.outlook.com/snds/index

Although, when I used free tool like MxToolBox to run your domain, looks like there's still some issue with dmarc and spf.

Answer 2

If you are experiencing a sudden and severe deliverability issue to Microsoft domains, it is important to follow these steps:

1. Check Blocklist Status: You can use the Office 365 Anti-Spam IP Delist Portal to check if your sending domain or IP address is on a blocked senders list. This portal allows you to request removal if you find that you are blocked.
2. Investigate Filtering Policies: Since you suspect that there may have been a recent policy change or filtering adjustment on Microsoft's end, it is advisable to check for any announcements or updates from Microsoft regarding changes in their email filtering policies. This information may be available through Microsoft support channels or community forums.
3. Maintain Communication: If the problem persists, consider reaching out to Microsoft support directly. Although external senders typically cannot open support tickets, you can ask the Microsoft 365 recipient to contact Microsoft Support on your behalf. They may be able to provide insights or assistance regarding your deliverability issues.
4. Monitor Authentication and Sending Practices: Ensure that your SPF, DKIM, and DMARC records are correctly configured and that your sending practices remain compliant with best practices for email deliverability. Regularly monitor your sending reputation and complaint rates to maintain a good standing.

By following these steps, you can work towards resolving the deliverability issues you are facing with Microsoft domains.

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References:

• External senders - Use the delist portal to remove yourself from the blocked senders list and address 5.7.511 Access denied errors
• External senders - Troubleshoot email sent to Microsoft 365