I have 100k+ unread email messages. Probably 2x that actually read. The only mail client that can handle my entire mailbox is outlook. And only up to outlook 20

I have 100k+ unread email messages. Probably 2x that actually read. The only mail client that can handle my entire mailbox is outlook. And only up to outlook 2013. I have used every mail client from lotus notes to thunderbird and all of them choke after reading 25% of my mailbox. Further outlook 2013 can handle all of this PLUS handle my various offline mailboxes going back to 1997. I obviously don’t like using an outdated mail client so will give this a shot and report back on my findings! Edit: the privacy policy is a nonstarter. This is not an offline application and the question of what happens to my data after acquisition is not answered satisfactorily. Back to the drawing board :)