I used to fan of yahoo mail 2-3 years ago, but after I purchased android phone, I was a need as you have to have one gmail account for your android device, after using this email service provider I can say that, it does all, I mean, you do not need any other account to do multiple activities, like you can use google plus with this email, you can sign up to facebook with this emai, if you want to sign in to youtube or would like to start your own youtube channel you do not need any extra email it for that, this single email id is enough.
It’s other features are: if you are talking about android phone you can backup all your data to google drive and if your mobile get misplaced or stolen, your data and contacts will be saved in that drive.
It is very light to load, you can open it easily in low speed connection also unlike yahoo or other email services. It is very easy to use, interface is very simple, even an uneducated person can understand it if we explain it to him/her.
It has hangout feature which work like skype, you can chat, can do voice and video calls, you also can send gifs everything.
Since you are using this email in your mobile you get notified whenever there is any email in your inbox, and yes, you can add as many accounts here.