How do I fix my email?
My email fails one or more of your tests.
XYZ company will not do business with us unless we pass your test(s).
You must secure your email system. Usually this means TLS encrypting email you send to others and accepting TLS encrypted email from others.
Securing your email system is outside the scope of our site. Try searching the Internet for "howto TLS" and the name of your email software, e.g. "Office 365".
You can also search the Internet for local consultants that can help you with your email system.