How to stop phishing Outlook calendar reminder popup

Hello Kevin M, thanks for posting this in our community.

These kinds of phishing events may contain malicious links or deceptive messages and often appear without any user action.

To report and block senders, right-click the event and choose Report as Junk or Report as Phishing. This helps Microsoft improve its spam filters. You can also block the sender by going to Tools, then Junk Email Preferences, and selecting the Blocked Senders tab.

You can also create a rule to move suspicious calendar invites to Junk before they reach your calendar. In Outlook Web, go to Settings, then Mail, then Rules. Click Add a new rule. Set the condition to Type equals Invitation, and the action to Move to Junk Email folder. Save the rule. This filters out spammy invites before they populate your calendar.

Hope this helps.

Kind regards,

John Oli

Is your problem the same as this one for Outlook Classic for Windows?
https://learn.microsoft.com/en-us/answers/questions/5597205/prevent-pfishing-calendar-items

If so, it is a known problem and there is nothing you can do on your Outlook client to stop it.

Hal Hostetler MVP-Outlook Volunteer Moderator Oct 28, 2025, 12:17 PM I and several other Outlook MVPs have experienced the issue, reported it to the engineering folks, and provided data. If you wish to report the issue yourself, for Classic Outlook go to Help > Contact Support and send them your data.

For Mac In App Support
https://support.microsoft.com/en-us/office/contact-support-within-outlook-for-mac-d0410177-8e65-4487-93f7-206a3a3d71a8

SPAM Calendar Events - Update 2025-12-05 - Still an ongoing issue. No update from Microsoft on a general solution.

If your organization has a Microsoft Defender for Office 365 subscription, there are steps your IT Admin can take to mitigate the impact:

https://techcommunity.microsoft.com/blog/microsoftdefenderforoffice365blog/strengthening-calendar-security-through-enhanced-remediation/4456876

If you are in an IT Managed environment, there are Mail Flow Rules that your IT Admin can implement that will block all external Calendar invites (and allow for specific exceptions):

https://learn.microsoft.com/en-us/answers/questions/5558001/how-to-prevent-calendar-invites-from-external-sour