JSFiddle - React, Tailwind, and code Playground

JavaScript

var a = document.createElement("div"); //create a wrapper
    a.innerHTML = '<p class=MsoNormal><b>Customer Email: <o:p></o:p></b></p></td><td width="\"75%\"" valign=top style=\'width:75.0%;border:none;padding:0in 0in 11.25pt 0in\'><p class=MsoNormal><a href="mailto:username@gmail.com">';
    document.write(a.innerHTML);
    var ps = a.querySelectorAll("p"); //get all the p tags
    var emails = [];
    [].forEach.call(ps,function (pTag) {
        var as= (pTag.querySelectorAll("a"));
         [].forEach.call(as,function(aTag){
            if(aTag.href && aTag.href.substring(0,7)==="mailto:"){
               //got a match
               emails.push(aTag.href.substring(7));
            }
        });
    });
    console.log(emails);