I used yahoo mail once and it as not upto the mark because their user interface is not good and it will mess up with everything and you will get frustrated soon so they need to work on the user interface a lot.
And yahoo mail also provides very less online data storage that is not sufficient for a professional that’s why the yahoo mail not even can think of competing with gmail services and also their are not so many utilities on their interface as compared with the gmail so after using yahoo mail for few days I left their services and again switched to the gmail services that is far better then the yahoo mail services.so finally I would suggest that yahoo mail need to work on the user experience and user handling.