Send & Receive Issues

How to Fix Exchange Blocking Microsoft Bookings Confirmation Emails

John Wilson Sep 28, 2026 868 views

Question details

External recipients are receiving Microsoft Bookings confirmation emails flagged as High Confidence Phish by the system.

How to Fix Exchange Blocking Microsoft Bookings Confirmation Emails

Product: Microsoft Exchange Online
Device & OS: not provided
Scenario: Sending Microsoft Bookings appointment confirmation messages to external clients or partners.
Observed behavior: Exchange Online is blocking the outgoing confirmation emails and incorrectly classifying them as High Confidence Phish.

Before you start

Ensure you have Microsoft 365 Global Administrator privileges, or know how to contact your organization's IT administrator, as resolving this backend routing issue requires elevated access to Microsoft Support.

Solution 1Recommended

Open a Service Request with Microsoft Support

Since the High Confidence Phish classification occurs on the Microsoft 365 backend, an administrator must request Microsoft Support to review advanced message traces.

When Bookings messages are aggressively filtered as phishing attempts, standard mail flow rules or safe sender lists are often overridden by backend security defaults. Microsoft Support has the necessary access to backend logs to identify the exact trigger causing the false positive and whitelist the internal routing.

Contact Your Administrator

If you are an end-user, notify your Microsoft 365 Global Administrator that external clients are not receiving Bookings emails.

Access the Admin Center

Have the Global Administrator log in to the Microsoft 365 admin center using their administrative credentials.

Navigate to Support

Click on 'Support' and then select 'Help & support' from the left-hand navigation menu.

Create a New Service Request

Open a new service request detailing that Microsoft Bookings confirmation emails are being blocked as High Confidence Phish. Provide recent examples, including sender, recipient, and timestamps.

Open a Service Request with Microsoft Support

Partner Support: Organizations using a reseller or federated partner for Microsoft 365 licensing should contact their specific provider if the internal administrator cannot open a direct request with Microsoft.

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Frequently Asked Questions

Why are my Microsoft Bookings emails being marked as High Confidence Phish?

This usually happens due to overly strict spam filter policies or anomalies detected by Exchange Online Protection (EOP) on the Microsoft backend. Since Bookings uses automated routing, EOP sometimes misinterprets these automated confirmations as malicious activity.

Can I whitelist Microsoft Bookings in Exchange Online myself?

Administrators can adjust anti-spam policies or create mail flow rules to bypass spam filtering for specific internal domains. However, if Microsoft's backend specifically flags the automated Bookings infrastructure as High Confidence Phish, those local rules are often bypassed, and a support ticket is required.

Who is authorized to open a support ticket for Exchange Online issues?

Only a Microsoft 365 Global Administrator or an authorized billing and support admin can open official service requests with Microsoft Support. Standard users must escalate the issue internally to their IT department.

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