Security Policy Errors

How to Bypass Spam Filtering with an Exchange Mail Flow Rule

Phi Hung Vo Oct 9, 2026 869 views

Question details

The user needs to allowlist a sender domain using a mail flow rule so that incoming messages bypass spam filtering and avoid the Junk Email folder.

How to Bypass Spam Filtering with an Exchange Mail Flow Rule

Product: Microsoft 365 Exchange Online
Device & OS: not provided
Scenario: Configuring email security policies in the Microsoft 365 admin center to prevent legitimate messages from a specific domain from being incorrectly marked as spam.
Observed behavior: The Microsoft 365 admin portal interface has changed, making it difficult for the user to find the specific option to bypass spam filtering for designated sender domains.

Before you start

Ensure you have the necessary Exchange Administrator permissions in your Microsoft 365 tenant to access the Exchange admin center and manage mail flow rules.

Solution 1Recommended

Configure a Mail Flow Rule to Set the SCL to -1

Modify message properties in the Exchange admin center to bypass spam filtering by setting the Spam Confidence Level (SCL) to -1 for a specific sender domain.

In updated versions of the Exchange admin center, the direct 'bypass spam filtering' checkbox may not be visible. Instead, administrators must manually instruct Exchange to bypass filtering by setting the Spam Confidence Level (SCL) to -1.

Open the Exchange Admin Center

Create a New Mail Flow Rule

Go to 'Mail flow' and select 'Rules'. Click on the '+' (Add a rule) icon and choose 'Create a new rule'.

Define the Sender Condition

Under 'Apply this rule if', select 'The sender', then choose 'domain is'. Enter the specific domain name you want to allowlist.

Set the Action to Modify SCL

Under 'Do the following', select 'Modify the message properties', and then choose 'set the spam confidence level (SCL)'. Set the value to '-1' to bypass spam filtering.

Save and Apply

Review the rule settings, choose the desired enforcement mode, and click 'Save'. The rule will now be active for the specified domain.

Configure a Mail Flow Rule to Set the SCL to -1

Rule Replication Delay: A newly created mail flow rule may take about an hour to fully propagate and apply to incoming emails across your organization.

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Frequently Asked Questions

Why are messages still going to the Junk Email folder after creating the rule?

It can take up to an hour for a new mail flow rule to apply across Exchange Online. If the issue persists after this time, verify that the rule conditions are correct and that no conflicting rules are overriding it. If needed, open a support request through the Microsoft 365 admin center.

What does setting the Spam Confidence Level (SCL) to -1 mean?

SCL stands for Spam Confidence Level. In Exchange Online, setting a message's SCL to -1 explicitly instructs the email filtering system to bypass all spam filtering checks for that specific message, ensuring it gets delivered to the recipient's inbox.

Can I bypass spam filtering for specific email addresses instead of entire domains?

Yes. When configuring the mail flow rule's condition in the Exchange admin center, you can choose 'The sender is this person' and specify individual email addresses instead of using the 'domain is' condition.

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