For a very useful, free desktop email client for Windows 10, try out Mozilla Thunderbird available for download from this website:
A number of desktop software programs need to be able to launch email clients, e.g. SliQ Invoicing requests Windows to launch an email client when you ask to email an invoice. In Windows 10, Microsoft have made this more difficult than in previous versions of Windows by no longer providing a free email client that supports a protocol called Simple MAPI for which free programs like Outlook Express or Windows Live Mail used to be available. A lot of people have bought Microsoft Outlook for email but, if you don’t have Outlook, we now recommend downloading and trying out Thunderbird as a free alternative.