Forum Discussion
Unified Company Calendar for Mixed Microsoft 365 and Non-365 Users – 2025
Seeking a Shared Calendar Solution for Mixed Microsoft 365 and Non-365 Users
I’m working on a solution to create a shared company calendar that everyone in our organization can view, while keeping editing permissions limited to a few selected individuals.
The challenge:
Some of our team members do not use Microsoft 365, and I’d like them to still be able to subscribe to or view the calendar and receive updates.
Ideally, this should work without requiring full Microsoft accounts.
I initially considered using an ICS-based calendar, but it seems Microsoft 365 Group calendars don’t support sharing via ICS links. I also explored creating a Group calendar as suggested in other threads, but ran into issues making it accessible to external users or those without 365 accounts.
For context, I’m a Global Admin, so I have full access to configure settings in the Microsoft 365 Admin Center and Exchange if needed.
We’re a small business, and our main goal is to have a centralized calendar for vacation schedules and company-wide events. It should be simple to access and maintain, with a focus on collaboration and accessibility across the board.
What I’m looking for:
- A calendar that’s viewable by all, including non-M365 users
- Editable only by a few delegated team members
- Compatible with Microsoft 365, but not dependent on it for basic access
- Any tools, workarounds, or best practices that have worked for others in similar hybrid environments
2 Replies
Hi Kidd_Ip
Thanks for your reply and suggestion!
I've implemented a similar approach in the interim, but I wanted to share a few observations that may be helpful for others navigating calendar sharing with external users. Hoping this post sparks further replies and long-term solutions!📧 Outlook on the Web – Permission Behavior
First note: While my interim solution is basically the one you posted (thanks again!), I wanted to mention that my Outlook on the Web sharing and permissions appear different from what you described.
Not sure if Microsoft made a recent change, but I do recall seeing the permissions you referenced in previous interactions. If anyone else has noticed changes or inconsistencies in calendar sharing behavior on Outlook Web, feel free to chime in.
⚠️ Key Limitations:
- Limited External Interaction
External users can view or subscribe to the calendar, but interactive features are not supported. - Event Response Visibility
RSVP responses from invited attendees do not appear in the calendar interface.
Email confirmations are inconsistent and may only reach the calendar creator. - Lack of Event Commenting
Subscribed users cannot comment or ask questions directly on events, which limits collaboration.
🔐 Microsoft 365 Group Calendars
Interestingly, I’m aware that external users can interact more fully when added as Guest accounts within Microsoft 365 Groups. This enables better calendar integration and RSVP tracking.
However, this approach introduces its own limitations:
- ❌ Public accessibility is reduced, as access is restricted to users with guest accounts.
- ❌ External users (e.g., Gmail users) must sign in with a Microsoft account or create one, which adds friction.
- ❌ ICS sharing is no longer an option in this scenario, removing the convenience of passive calendar subscriptions.
🏛️ Insight from a User: Potential for Better External Calendar Integration
A key user for the client I represent, who previously held a role within a state government organization, stated that their calendar environment supported more seamless collaboration with external email addresses, including Gmail and Google Workspace.
Their setup was reportedly based on Microsoft 365 or Exchange, and included:
- ✅ RSVP visibility from external attendees
- ✅ Limited interaction capabilities for non-Microsoft accounts
This insight suggests that with the right configuration or integration, Microsoft’s ecosystem may offer enhanced calendar sharing functionality beyond what is currently achievable through ICS links.
💬 Final Thought
While ICS sharing works in the short term, it’s clear that it comes with trade-offs—especially when working with external users who expect more interactivity. If anyone has experience with alternative setups, third-party tools, or configuration tips that improve external calendar collaboration, I’d love to hear your thoughts.
- Limited External Interaction
You can consider this as publishing a shared calendar via ICS\HTML:
- Create a Dedicated Shared Calendar
- Use Outlook desktop or Outlook on the web to create a new calendar (not a Group calendar).
- Name it something like “Company Events” or “Vacation Tracker.”
- Delegate Editing Permissions
- In Outlook, right-click the calendar > Properties > Permissions.
- Grant Editor or Owner access only to selected M365 users.
- Set Default permission to “Reviewer” or “None” to prevent unintended edits.
- Publish the Calendar to Web
- In Outlook on the web:
- Go to Settings > View all Outlook settings > Calendar > Shared calendars.
- Under Publish a calendar, select the calendar and choose:
- Can view all details (for full visibility)
- Get ICS link (for subscription)
- Get HTML link (for browser view)
- Share the ICS and/or HTML link with non-M365 users.
Please note, this method does not require recipients to have Microsoft accounts and works with most calendar apps such as Apple one
