Issue with Outlook Calendar

Question

Switched over to new outlook because could no longer use classic due to an error was constantly getting when trying to send or get mail it said the message store has reached its maximum size so switching to new outlook got a new error when trying to edit calendar. Something went wrong we couldnt save your calednar event. please help

Answer 1

Hi @Peter Alexandris,

Welcome to the Microsoft Q&A forum. Thank you for reaching out and for sharing the screenshots.

Based on the error messages shown, this issue may be related to the mailbox storage reaching (or being very close to) its maximum size. When this happens, Outlook may block not only sending and receiving emails but also changes to other mailbox data such as calendar events. In the new Outlook, this can appear as a generic error like “We couldn’t save your calendar event.”

To help narrow this down and potentially resolve the issue, you may try the following:

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1/ Check your mailbox usage

Sign in to Outlook on the Web and verify whether your mailbox shows as full or close to the limit by:

• Select Settings (gear icon) in the top‑right corner > Account > Storage.
• If the mailbox is close to the storage limit, Outlook can sometimes prevent calendar edits. Freeing up space by removing older emails and emptying Deleted Items may help resolve this.

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2/ Test calendar editing in Outlook on the web

If you’re able to create or edit calendar events successfully in Outlook on the web, but the same action fails in the new Outlook app, this generally suggests that the issue may be specific to the app rather than the mailbox itself.

In this situation, you can try restarting the new Outlook app and signing out and signing back in to refresh the app’s connection. These steps may help resolve temporary sync or session-related issues within the app.

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3/ Contact Microsoft Support

If the issue persists after applying these steps, it may require a deeper technical review. The best next step would be to have your IT administrator open a support ticket with Microsoft via the admin center. A technical support engineer can then initiate a remote session, review backend settings, and run diagnostics. If needed, they can escalate the case to specialized engineering teams who are well-equipped to perform advanced troubleshooting and provide targeted solutions.

As moderators, our primary goal is to provide helpful guidance and support through general troubleshooting steps. While we don’t have access to internal systems or administrative tools required to resolve account-specific or backend issues, we truly appreciate your understanding of these limitations. We genuinely hope the information we share helps point you in the right direction, and we're always here to assist as much as we can within our scope.

For guidance on how to request support in the admin center, please refer to: Get support - Microsoft 365 admin. 

I hope this information is helpful. Thank you for your patience and understanding. If you have additional questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.

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