Lost my E-Mail, how can I get it back?

Recently, I lost my Hotmail that I've had since 2005/2006 (A decade). This email is incredibly important for me, and nearly every important thing I've ever registered on has been registered with this E-Mail. I can't get support from Outlook/Microsoft, not a single phone number I find is woking, and I can't reset my account because my now-dead mother made It and I don't know the security question. I've tried everything I can, and I really need It back. Steam, Origin, Battle.net, all of that is on this E-Mail and I can't access any of It before I get it back, does anyone have any idea how? Please? PM me if so.