I can login in my account but I cannot access mail

I can login in my account but I cannot access mail

I have a very rarely @zoho.com used account. I can login to that account and when I login I can use anything active EXCEPT for the mail. When I select the mail it asks me configuration data for an external account (I don't want an external account, I want the @zoho.com personal account)

If I sent an email from a different account, I get

550 550 5.1.1 <xxxx@zoho.com>... User unknown (state 13).

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