Security Policy Errors

How to Prevent Exchange Online Allow List Entries from Expiring

Maira Mehtab Sep 20, 2026 869 views

Question details

Administrators need to configure Exchange Online Protection so that permitted entries on the allow list do not automatically expire each month.

Product: Microsoft Defender for Office 365
Device & OS: not provided
Scenario: Managing email security, spam bypass rules, and maintaining a stable Tenant Allow/Block List without manual monthly renewals.
Observed behavior: Exchange Online Protection allowed entries expire on a monthly basis, forcing administrators to repeatedly recreate or renew them.

Before you start

Ensure you have the appropriate Security Administrator or Global Administrator privileges in the Microsoft 365 Defender portal to modify Threat Policies.

Solution 1Recommended

Configure Extended Expiration in Microsoft Defender

Use the Microsoft 365 Defender portal to extend the expiration date of allow list entries or set them to never expire where supported.

Microsoft Defender for Office 365 automatically assigns expiration dates to allow entries to prevent temporary security bypasses from becoming permanent vulnerabilities. However, for trusted internal tools or critical partners, you can manually extend this period.

Access the Microsoft 365 Defender Portal

Open your web browser, navigate to the Microsoft 365 Defender portal, and sign in with your administrative credentials.

Navigate to the Allow/Block Lists

Go to 'Policies & rules' in the left-hand navigation menu. Select 'Threat policies', then look under the 'Rules' section and click on 'Tenant Allow/Block Lists'.

Edit the Entry Expiration

Locate and select the specific allowed entry you want to modify. Click the 'Edit' button in the flyout pane. Change the 'Expiration date' to an extended future date, or select 'Never expire' if the option is available for that specific entity type.

Save and Review Policies

Click 'Save' to apply the changes. It is highly recommended to periodically review all permanent allow entries to ensure they still comply with your organization's security posture.

Free Microsoft Office alternative

Looking for a Seamless Office Suite for Your Organization?

While managing Exchange server security is a Microsoft 365 administration task, if your organization is looking for a lightweight, cost-effective daily productivity suite, WPS Office provides an excellent alternative. It offers powerful document creation and editing capabilities without the heavy subscription fees.

1. Download WPS Office: Visit the official WPS website and click the free download button for your operating system.
2. Install the Software: Run the lightweight installer and follow the on-screen prompts to set up the software in minutes.
3. Open Your Documents: Launch WPS Office and instantly open your existing Microsoft Office files with zero formatting loss.

Fully compatible with Microsoft Office formats (.docx, .xlsx, .pptx) to ensure smooth collaboration.Lightweight installation and resource-friendly performance on all operating systems.Includes Writer, Spreadsheet, Presentation, and a versatile PDF editor in a single familiar interface.Cost-effective solution, reducing software overhead while maintaining high team productivity.

microsoft office alternative - wps office

Frequently Asked Questions

Why do Exchange Online allow entries expire by default?

Microsoft enforces default expiration limits (usually 30 days) on allow list entries to ensure that temporary bypasses for spam, phishing, or malware filters do not become permanent vulnerabilities. This encourages administrators to fix the root cause of false positives rather than permanently bypassing security checks.

Can I set all Tenant Allow/Block List entries to never expire?

No, the 'Never expire' option is not universally supported for all entry types. Its availability depends on what you are allowing (such as domains, email addresses, files, or URLs) and your organization's specific Microsoft Defender for Office 365 security policies.

What happens to emails if an allow list entry expires?

Once an allow list entry expires, Microsoft's default filtering mechanisms resume control. If the sender, IP, or URL was previously triggering security filters, future emails containing them may be blocked, sent to junk, or quarantined until a new allow entry is created or the underlying issue is resolved.

How often should I review my Exchange allow lists?

Security best practices dictate that administrators should review their Tenant Allow/Block Lists at least quarterly. This ensures that only necessary entries are maintained, keeping the organization's email environment secure against evolving threats.

Microsoft Office Security Issues