Even though many still have yet to hear of it. It's one of the top "cross platform" email clients because it can be used on Mac, Windows, Linux, operating systems. It can be used to download AOL, Yahoo, GMail and other large mail providers using IMAP and avoid their webpage interfaces, often loaded with advertisements. I use with Yahoo to avoid their horrible webmail interface and all it's adverts. Basically, if you have any webmail, it can be set to download it into separate folders for each user, or dumped all into common Local Folders, your choice. If you set each account in it separate, you can also connect to the SMTP servers and use it for both receiving and sending from those online mail providers, without needing to use their webmail interface for either purpose.
Dec 2015 ratings on email client usage.
https://emailclientmarketshare.com/