Google about this and there is plenty of information about restoring Windows Live Mail.
Although it still works with pre-Win10 OS MS have not supported it since 2017 and no longer provide a Windows Live Essentials or or separate Windows Live Mail downloads since then.
There are some apparently OK sources for it but reports of plenty of dodgy ones too. I found a Live Essentials installer on the internet archive site Wayback Machine which was linked too direct from a MS Community forum post. Whether it is safe or even works I have no idea. On your own head whatever you do.
Better to use a more up to date e-mail client now, Outlook or Mozilla Thunderbird being the most obvious ones to try.