How to Allow Bulk Sender Messages Instead of Quarantining Them in M365
Question details
Need to bypass quarantine and allow message delivery from legitimate bulk email senders without altering the global Bulk Complaint Level (BCL) threshold.
- Product
- Exchange Online
- Device & OS
- not provided
- Scenario
- Messages from trusted bulk senders, such as internal help desks or automated systems, are being flagged by the bulk anti-spam policy and sent to quarantine.
- Observed behavior
- Legitimate bulk messages are blocked and quarantined by Exchange Online due to high Bulk Complaint Level (BCL) ratings rather than standard spam signatures.
Ensure you have Exchange Administrator or Global Administrator privileges in Microsoft 365 to modify mail flow rules and access the Microsoft 365 Defender portal.
Add the Sender to the Microsoft 365 Anti-Spam Allow List
The most direct way to bypass quarantine for specific trusted domains or senders is to explicitly add them to the inbound anti-spam policy allow list.
Adding a sender or domain to the allowed list tells Exchange Online Protection to bypass spam filtering for that specific address. This ensures that their bulk emails are delivered straight to the Inbox instead of the quarantine queue.
Navigate to the Microsoft 365 Defender portal at https://security.microsoft.com/antispam and log in with your administrator credentials.
Click on 'Anti-spam inbound policy (Default)' or your organization's custom inbound policy. In the properties pane that appears, scroll down and click 'Edit allowed and blocked senders and domains'.
Click 'Allow senders' or 'Allow domains', enter the trusted email addresses or domain names generating the bulk emails, and save your changes.
Create a Mail Flow Rule to Reset the BCL Value
If you need more granular control over message delivery, you can use a mail flow rule to manually set the Bulk Complaint Level to 0 for specific senders.
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Frequently Asked Questions
What is the Bulk Complaint Level (BCL) in Microsoft 365?
BCL is a rating from 1 to 9 assigned to bulk mailers by Exchange Online Protection. Higher BCL values indicate that a sender is more likely to generate user complaints, which often results in their emails being routed to quarantine or the Junk Email folder depending on your anti-spam policy settings.
Why did my internal help desk system's email get quarantined?
Automated systems like help desks or marketing platforms often send high volumes of similar emails. Microsoft 365 evaluates these as bulk mail. If the system's BCL score exceeds your organization's established threshold in the anti-spam policy, Exchange Online will quarantine the messages.
Is it safer to change the global BCL threshold or use an allow list?
It is significantly safer to add specific trusted senders to your anti-spam allow list or use targeted mail flow rules. Lowering the global BCL threshold makes your entire organization more vulnerable to unwanted spam and promotional clutter from untrusted bulk senders.
