Many missing emails

Many important emails that I had stored in my inbox, rather than kill trees, are suddenly gone.  All my 2024, 2025, 2023 and are gone.  I called xfinity and they have no idea why this is happening.   I also spend about an hourna day purposely filling my Trash and deleting them to try and stay ahead of maxing out my storage.  

They say only solution is to restore my deleted emails,  which will make situation worse.  I will get my Trash back, max out available capacity and still be missing my emails.  

It is nearly as important to know why this is happening and find a way to stop it, as it is to restore them, especially since they can not selectively bring back the inbox ones rather than deleted ones.

Are there any alternatives to xfinity,  who has no solution?  Like a local tech expert or any thing?  I have to get the emails back.

Help!!!