Choosing the right email client is more important than it seems. Each one comes with different features and storage and you should pick one that suits your needs. For example, a work account might require better organisation functions, while if it is a personal account you might also want advanced features like messaging.
Yahoo Mail used to be the most popular email client back in the day. If you have a Yahoo email account, you will receive 1 TB of free storage. Yahoo Mail does not allow you to attach files over 25 MB, but you can do that via Dropbox or Google Drive without leaving your message.
Yahoo Mail is customisable and it allows you to change your own background and color scheme. Additionally, it allows you to create 500 addresses that are linked to your main address. These addresses are disposable, which means that you can delete them if you don’t need them anymore.
Google’s email service is one of the best. It comes with plenty of features and a nice 15 GB storage. Gmail is also customisable and it also allows you to organise your emails better than any client. You can use labels and filters for them and Gmail will automatically sort them for you.
If you get Gmail Offline, you will be also able to access your messages even when you do not have an Internet connection. Also, you can use Google Calendar to schedule events taken from your messages.
This is an alternative that is less known. It comes with 10 GB of cloud storage and it allows you to import images by the URL, send a SMS copy of an email and get notifications if someone does not reply to an email.
Yandex also shows the online profile of the persons who send you an email, so you can see exactly who is that person.