I have a user in my organization that uses Windows Live Mail 2012 on Windows 10.
Among the features needed are connecting to arbitrary e-mail servers, handling multiple accounts, having folders, marking of priority e-mails to be read later, working with that "tell I read the e-mail" feature, and most importantly of all features: supporting multiple signatures.
Microsoft is trying very hard to kill WLM, it is "not supported" in Windows 10, their e-mail servers don't communicate with it, and they launched an update in december that broke the software completely... That particular update is NOT installed, but WLM today kept freezing randomly all the time on the machine.
The thing is, I personally never used e-mail clients such as this, even WLM I am not much sure how to use... So I am completely clueless on what to do.