Calendar Problems

How to Share an Internet Calendar with All Outlook Users

Amos Gikunda Sep 30, 2026 869 views

Question details

An administrator needs to automatically subscribe all users in an organization to a specific Internet Calendar via an ICS URL.

How to Share an Internet Calendar with All Outlook Users

Product: Microsoft Outlook / Microsoft 365
Device & OS: not provided
Scenario: Distributing an Internet Calendar (ICS) centrally so that all enterprise users have access without manually adding it individually.
Observed behavior: There is no direct Microsoft 365 API or built-in admin tool to automatically push an ICS subscription to all individual users' Outlook accounts.

Before you start

Ensure you have Microsoft 365 Exchange administrator privileges, as you will need to create a shared mailbox and manage delegation settings.

Solution 1Recommended

Use a Shared Mailbox Workaround

Since there is no direct API to push an ICS file to everyone, the most practical approach is creating a shared mailbox and subscribing to the calendar from there.

This method creates a central point for the calendar. By granting users access to the shared mailbox, they can view the Internet Calendar without needing to subscribe individually.

Create a Shared Mailbox

Delegate Access to Users

Add the required users as members to this shared mailbox. Note that you must add individual members, as nested groups may not be fully supported for shared mailbox access.

Open Outlook on the Web (OWA)

Log into Outlook on the web with an account that has access, click on your profile picture, and select 'Open another mailbox' to access the newly created shared mailbox.

Subscribe to the Calendar

Navigate to the Calendar view in the shared mailbox, select 'Add calendar', choose 'Subscribe from web', and enter the ICS URL.

Check Delegation Permissions: Carefully configure delegation in the Exchange admin center. Adding users to a shared mailbox can sometimes grant 'Send As' permissions, which you may want to restrict.

Solution 2

Submit a Microsoft 365 Service Request

If the shared mailbox workaround does not meet your organization's administrative or security requirements, you can escalate the inquiry.

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Frequently Asked Questions

Can I use PowerShell or an API to push an Internet Calendar to all Outlook users?

Currently, there is no direct Microsoft 365 API or PowerShell cmdlet that natively subscribes all individual users to a single Internet Calendar (ICS) URL automatically.

Can I assign a Microsoft 365 Group to a shared mailbox for calendar access?

No, groups and shared mailboxes are different types of Microsoft 365 entities. You cannot directly add a group to a shared mailbox; you must add members or manage delegation via the Exchange admin center.

Does sharing a mailbox calendar give users 'Send As' permissions?

Yes, depending on how you delegate access to a shared mailbox, it can inadvertently grant 'Send As' permissions to the users. You should carefully review and edit the delegation settings in the Exchange admin center to prevent unauthorized email sending.

Outlook & Email Problems