StartMail.com ( https://www.startmail.com/ ) is a subscription e-mail service from the Netherlands where investigating an account must be ordered by a Dutch court of law, not a request by the United States or another nation. The service was created by the makers of the Internet search engine StartPage.com ( https://www.startpage.com/ ). The annual StartMail.com subscription price is $59.95 US. It is considered one of the planet's most secure e-mail services.
If you are knowledgeable enough to send and receive encrypted messages, StartMail.com makes it very easy by creating key pairs and even embedding public keys within each message's signature.
As dcj123 has written, using a long, complex password is important. NSA leaker Edward Snowden uses passwords that he can't even remember (but knows where to find them). So, if you choose the complex password method, use Strong Password Generator ( https://strongpasswordgenerator.com/ ) and plan to keep a list of your accounts and passwords within a text file which you save on your computer away from the browser, and print out as a backup.