generate-emails.js

function makeEmail() {
    var strValues="abcdefghijklmnopqrstuvwxyz";
    var strEmail = "";
    var strTmp;
    for (var i=0;i<10;i++) {
        strTmp = strValues.charAt(Math.round(strValues.length*Math.random()));
        strEmail = strEmail + strTmp;
    }
    strTmp = "";
    strEmail = strEmail + "@";
    for (var j=0;j<8;j++) {
        strTmp = strValues.charAt(Math.round(strValues.length*Math.random()));
        strEmail = strEmail + strTmp;
    }
    strEmail = strEmail + ".com"
    return strEmail;
}

var emails = []
for (var i=0; i<100000; i++) {
  emails.push("  '" + makeEmail() + "'");
}

print("var EMAILS = [")
print(emails.join(",\n"))
print("]\n")

Execute this via mongo shell and pipe output to emails.js:

mongo --quiet generate-emails.js > emails.js