I thought this was very hopeful. I have been having this issue since November 2023 and most spam invitations span months! I can click Decline and it goes a way...for a minute, then takes over my calendar again. I do have an associated email with mine, it seems others do not, or maybe their email goes directly to their spam folder and they don't see it. I looked into the Rule solution, but don't see an option for "suspicious or unknown" senders. It wants me to enter an actual email. But they are all different and have different topics! (Paramount+, Peacock, AARP, and many more) I finally figured out that if I delete the cal invite on my Outlook (web) account on my computer, it would go away on my computer and my phone. Finally figured out how to delete on my phone without having to go to the computer. I do not have a delete option when I open the calendar invite, but if I don't open it and do a long tap, then a Cut option comes up. That works. But the real solution would be to prevent it from putting these bogus calendar invites on my calendar in the first place. I do not have a "File" to click on in the web browser version of Outlook, so I opened the Outlook app on my computer which does have a File menu. I navigated to and turned off the option to "Automatically process meeting requests and responses..." Then I texted a friend about what I had found. As soon as I sent the text, I got a meeting notice from Elon Musk's Portable Heater Team! Maybe it takes longer than sending a text to take effect. I will give it a chance and report back.