Unable to verify account name or password

I cannot receive or send mail, I have tried everything to get this to work . I have worked with my provider to make sure I have entered the correct info. Deleted the account and tried to create a new account re-entered the data on both incoming and out going server, restarted my mac, catalina version 10.15.7.

In mail when I enter my email address lmiller@*** and password it instantly gives an error Unable to verify account name or password which I believe might be a code problem that came down with one of the updates. As I have not had this problem before. I would really like to get this fixed it's frustrating .

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