Thank you to all who tried to help me!
Finally was able to configure. It was not a Firewall nor Modem/Internet Issue.
It was Yahoo. It seems that now you have to create a third party email password which is given by yahoo. (I do not remember doing this before). Indicate the name of the third party (Manager) After the PW was generated I entered it in the PW box provided in Manager and Violá!
Thanks again and Happy Holidays!!!