If it is located in the USA, the Feds, alphabet, and “law enforcement agencies” can and will clandestinely access it. There is no privacy and there are no secure Internet domains here in the USA. That is why we have used Fastmail, located in Australia for over two decades.
After a lot of research and trial and error, I chose not to host my own email server. Instead, I chose an incremental step of separating my personal and work email. I migrated my personal emails to Australian-based FastMail. The company claims to be free of NSA surveillance. I’ve also appreciated the mental separation between work and personal communications that two email accounts provides.If you want increased peace of mind, another option is Norwegian Runbox, which promotes itself as secure offshore email for companies, organizations and individuals. It encrypts your email and supports built-in PGP encryption options.
So we have ProtonMail, FastMail, and Runbox as good alternatives.