This may be a security issue.
Who is the account provider?
What type of device are you trying to set up the email account on?
Ok, this is very unusual... let me see if the other experts have any idea on a workaround for this.
sorry that was for another question. I googled yours and the only thing i could find on that error was somebody trying to use a postoffice.net account with outlook 365 it might have been you.