emails are being deleted from Mail-Calendar app

Randomly emails, generally groups of emails by date, suddenly disappear. I keep both email accounts that I use uncluttered and none of the folders are any where near being full. Here are two examples. I have an account from Primus. I transfer some emails from the inbox to a folder called receipts. That folder is an archive of important messages concerning purchases, reservations etc. Suddenly two days ago every entry from February 11 to today disappeared. They were not magically moved to a different folder, they are gone. I also have my Gmail account available in Mail-Calendar. Today all items except one in the Inbox disappeared. This was actually fortunate becasue I could go to Google Chrome open my Gmail account and see that my Inbox is intact. Once again I looked in every folder and the emails have vanished. If my Gmail account is fine if I go online to access but things are lost in Mail Calendar I assume that the problem is the windows app.
I don't want to install a third party email app because I want the functionality of People to be available. However I will certainly give up on the Windows app if my emails are not secure.
any help would be greatly appreciated

Welcome to the forum, That is a new one on me, I tried it a while back and had a lot of sync issues (11 was new then) so I went back to Outlook from the Office 2019 Pro Plus package

To #2, thank you for the reply.
I don't have many options. I have Home and Student Office 2019 and Windows 11 Home, so i don't have Outlook Pro packages to roll back to. There is only one other computer syncing at this time, it shows identical results. I have tried to phone Microsoft for help with no avail, no answer from a human being after 60 minutes actually, and the insane 'help robots' should be vapourized.
Should I go to a third party program and forget about Mail and Calendar?
I have lost enough important emails to this point that I could scream. If you can't save a an email for a few weeks with some comfort of security then the app is faulty. Do you agree?

I have no choice but to give up on finding a solution to repair Mail and Calendar. At this point I cannot trust it to safely store important emails which makes it unusable for me.
Can anyone suggest a third party email program that I should change to. I have looked at reviews but none of them specifically state the compatibility with windows 11. I have been using the Mail app for years and problems only began after I changed to win11, so it is my number one suspect.
thanks for any advice

vallero said:

Can anyone suggest a third party email program that I should change to. I have looked at reviews but none of them specifically state the compatibility with windows 11. I have been using the Mail app for years and problems only began after I changed to win11, so it is my number one suspect.
thanks for any advice

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I use Thunderbird with Win 11 and it works well, free and full-featured.

thanks Trevo, I will look at it