Outlook 365 - can’t cancel event

Question

I have access to a supervisor’s account in order to schedule events, and am able to schedule and update new events on their behalf. However, I am unable to update/cancel events created on the supervisor’s behalf by a previous employee who had the same permissions I do now. The events appear with my supervisor as the organizer, and when I attempt to, for example, cancel, I get the cancellation message followed by a message saying “the event could not be deleted.” Similarly, if I update an event other attendees do not receive the update. This happens in both the O365 web and desktop client.

Answer 1

Hi @Seth Hooker 

Welcome to the Microsoft Q&A forum and thank you for reaching out to us.   

I appreciate the clear details you shared. When cancellations don’t complete and updates aren’t delivered, particularly on a supervisor’s calendar. 

From experience, these symptoms most often show up with meetings that were originally created by a previous delegate or on calendars that still use an older sharing/delegation model. In those cases, Outlook/Exchange can block deletes or route updates differently.  

Let’s walk through a concise plan that tends to resolve this scenario, step by step. 

To keep things straightforward, here are some steps you can consider: 

1) Confirm you have the right permissions on the supervisor’s mailbox 

You’ll want both: 

• Calendar folder: Editor (with “Can view private items” if needed). 
• Mailbox-level: Send As or Send on behalf of for the supervisor (cancellations or updates must be sent from the organizer identity). 

Outlook and Exchange only lets the organizer send cancellations or updates. Delegates can do that, but only if they can send “as” or “on behalf of” the organizer; calendar folder rights alone aren’t sufficient.  

How to verify in the Exchange Admin Center (admin needed): 

• Go to the Exchange Admin Center  
• Recipients → Mailboxes → Choose the account → Mailbox delegation: Check Send As and Send on behalf lists. Add your account if missing. Then confirm your Calendar permission level is Editor in Outlook/OWA.  

If the previous assistant created some meetings using Send As, cancellations now may require you to have Send As (not just “on behalf”). In many orgs, admins grant both to executive delegates to avoid edge cases.  

You may find further guidance here: Manage permissions for recipients in Exchange Online   

2) Re-add the delegate relationship cleanly 

• Stale or multi-delegate setups can confuse meeting processing. Best practice is 1–2 delegates and ensure the delegate receives meeting-related messages.  
• Recreate via OWA (recommended) and tick “Let delegate view private events” as needed. Managing  
• OWA path (for the supervisor, or an admin with access):  Go to Calendar → Sharing & permissions → Add your address → choose Delegate and enable the private-events option. This uses Microsoft’s newer, more reliable delegation flow. 

Here’s a resource that provides more insight: Managing Delegates in Outlook 

Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link    

3) Send a test update/cancellation as the supervisor 

Open one of your newly created meetings (that you know you can manage) and: 

• In Outlook, set the From field to the supervisor’s address and send an update; or cancel the test meeting. 
• Confirm the outbound message shows “Supervisor” (or “You on behalf of Supervisor”) and attendees receive it. This validates your Send As / on behalf path end-to-end. 

To learn more, please visit: Send As vs Send on Behalf vs Full Access permissions 

Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link 

4) Account for “Shared Calendar Improvements” 

Microsoft moved a lot of update logic to the server; prompts may not appear and updates behave differently, especially for attendee-only changes.  

If you suspect odd update delivery, try toggling the feature in classic Outlook or use OWA/new Outlook where server-side behavior is expected.  

• When enabled, Exchange can auto-send updates (and sometimes file them into Deleted Items), which can look like “no one received anything” when, in fact, processing happened silently.  

Additional details are available at the link below: 

• Send Update To Attendees Prompt Not Displayed When Updating Meetings - Outlook | Microsoft Learn 
• Exchange Online Calendar Auto-Processing Vexes Some Users - Petri IT Knowledgebase 

Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link 

5) Check mailbox storage and recoverable Items on the supervisor 

If the supervisor’s mailbox (especially Recoverable Items) is full, deletions and cancellations can fail with messages like “could not be deleted.”  

Enabling archive with auto-expanding resolved exactly this for others. Your IT can review quotas and enable archiving.   

Additionally, as other users have raised similar concerns and may not be aware of where to share their feedback, I hope this response helps clarify the situation and suggests a potential next step. Highlighting this information can make it more visible to others in the community who may be facing the same issue, making it easier for them to find guidance and contribute their feedback as well.

Thank you again for your time and for raising this important usability concern. If you have any further questions or need additional assistance, please don’t hesitate to reach out.

I look forward to your thoughts on this. 

Wishing you and your family a joyful and prosperous New Year.   

 

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