Mac Mail email content keeps disappearing and will not load

I have had this issue for over year now and its driving me insane.

the content of emails in my inbox take 10 - 20 minutes to show up and it makes using Mac mail impossible.

I have followed so many supposed fixes and none of them last more than a day or so, then it does it again. I have uninstalled and reinstalled Mac mail and the entire OS, I have shut down opened up mail so many times to reboot it, I have deleted certain files that force mail to rebuild and that still doesn't last long..

WHY OH WHY CAN'T APPLE FIX THIS **** UP !!!!! Its not a new thing we ALL Know it's an issue.