Mail continues to switch me to Outlook - how do I disable?

Thanks for your help! I do not walk on water but I do part it.

My dude here has the answer. I have tried everything and nothing worked. I did what he said. It took a little doing because you have to remove all inherited permissions from the folder. After you remove all inherited go back and add yourself and administrator and change those permissions to read only and bam, no more switching. It doesn't stop it from downloading Outlook but it does stop it from switching automatically and it also stopped it from replacing my mail shortcut on the taskbar. You my friend walk on water too I bet. Thank you, I hope others see this response and it helps them too.

It looks that we have no choice but to find a substitute for Mail if we don't like Outlook. I have tried Thumderbird but I find it quite slow to open and doesn't manage Outlook calendars. After some search and experiments, I finally found Wino Mail which looks very much like Mail (and VERY FAST to open!) and One Calendar which is very fast too and very convivial. And both are FREE !

Yes! It reminds me of a virus that just keeps trying to install after every deletion. I wish I had the funds to buy a really good external hard drive to install Linux on. I tried Peppermint OS for a year back before Covid and I loved it. But I'm tied to Windows because of the software I use for work. Crossover Linux worked beautifully for many of my other software programs for Windows but the main one I use for work is proprietary. But as soon as I retire, I'm going back. Crossover Linux is a godsend. Again, good luck to everyone having this issue. I'm so happy I moved on to Thunderbird Calendar.

Thanks I don't use the Calender much so that's not an issue. I pay for office 365 so I can use that. The problem is my that a 92 year old family member that piggy backs on my 365 account as allowed has always use windows mail the in built app that came with windows 11 10 and earlier. Microsoft take no account of very old peoples struggle with change and just keep changing things. Ie moving the start button and programs location on windows 11. I realise change is good but why not leave a "Classic" option for those that struggle. Microsoft are very thoughtless and have become more selfish in recent years. I have considered Thunderbird but in recent time MS have started bombarding people with non native apps to switch. MS is becoming more and more like a virus. If I was starting from scratch I would probably go for Linux.