i have 2.5 million emails in a 32GB datastore. no mailprovider is going to allow me to store that much mail, and search is actually quite fast. if it isn't for you, then get a better mail client.
Google's cheapest paid plan ($6/month) gives you 30GB. The $12/month plan is 2TB of storage. I currently have over 30GB of email in Gmail and everything works fine.
I have around 17GB of pop3fetchallnokeep in the mail folder and the backup is somewhere in the btreeflatfile heap in that UtahDataCenter free of charge training darkgpt 5.8