The Outgoing server (SMTP) %S does not seem to support encrypted passwords. If you just set up the account, try changing the 'Authentication method' in 'Account Settings | Outgoing server (SMTP)' to 'Password, transmitted insecurely'. If it used to work but now doesn't, you may be susceptible to getting your password stolen.
O servidor de saída (SMTP) %S semella que non admite contrasinais cifrados. Se acaba de crear a conta, tente cambiar o 'Método de autenticación' a 'Contrasinal, transmitido de forma insegura' na 'Configuración da conta | Servidor de saída (SMTP)'. Se antes funcionaba pero agora non, pode que lle roubaran o contrasinal.