why won't thunderbird accept netscape as an email address?

What happens when you try? Please quote any error messages you see precisely and in full. Netscape is now owned by AOL, which is now owned by Yahoo. How that complicates things, I shudder to think. I found this page that describes AOL/Netscape's proper email server settings. I have no idea how old this article is or if it's still accurate: https://help.aol.com/articles/update-netscape-isp-account-info-in-third-party-email-applications Thunderbird will make a guess at the proper settings when you use its automatic setup wizard ("Account Hub"). If it doesn't guess correctly you will have to manually enter the server settings, which should be available from the provider.