That are a lot of different questions:
1. What is the best e-mail provider?
2. What is the most secure e-mail provider?
3. What is the best way to access and that mail (pop3 or imap-client, webmail, Exchange protocol)
4. What is the most secure way to access and that mail (pop3 or imap-client, webmail, Exchange protocol)
5. What is the best pop3 or imap client?
6. What is the secure pop3 or imap client?
7. What is the best browser to use for webmail?
8. What is the most secure browser to use for webmail?
9. Is MS Outlook a good and secure program to access an MS Exchange server?
10. What is the best host for hosted Exchange?
11. What is the most secure host for hosted Exchange?
And, curiously enough, none of those 11 questions have to do with Windows 10.
What is the best, most secure, email program/service to use with Win 10 other than one of microsoft's and/or google?

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