Fixing Microsoft Defender for Office 365 Safe Attachments Policy Gaps: A Guide for Security Admins

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Understanding Safe Attachments Policies in MDO365

Safe Attachments policies in MDO365 help protect your organization from malicious email attachments. However, common policy gaps can allow potentially dangerous files through.

Common Policy Gaps to Address

It’s essential to regularly audit and adjust your Safe Attachments policies to avoid security breaches. Some common policy gaps include:

• Exclusion of specific file types: Excluding certain file types from scanning can create vulnerabilities.
• Insufficient user training: Users may not understand the importance of Safe Attachments policies, leading to careless behavior.

Checking Safe Attachments Policy Scope and Exclusions

To ensure your policies are as effective as possible, review the scope and exclusions regularly. You can do this through the MDO365 portal:

1. Sign in to the MDO365 portal.

2. Navigate to 'Policies & rules' > 'Threat policies' > 'Safe Attachments.'

Dynamic Delivery Mode and Its Impact on Email Flow

Dynamic Delivery mode helps improve email delivery times by sending safe emails directly to users’ inboxes, while suspicious emails are sent to a quarantine. Enabling Dynamic Delivery can help avoid delays in legitimate email deliveries.

Testing Safe Attachments with EICAR Test Files

To confirm that your policies are active and functioning correctly, use EICAR test files (a harmless file designed to simulate a virus). Send these files as email attachments and verify if they’re blocked or delivered.

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