javascript:(function(){
    let saveBlob = (function () {
        let a = document.createElement("a");
        document.body.appendChild(a);
        a.style = "display: none";
        return function (blob, fileName) {
            let url = window.URL.createObjectURL(blob);
            a.href = url;
            a.download = fileName;
            a.click();
            window.URL.revokeObjectURL(url);
        };
    }());
    let a = document.querySelectorAll('a');
    let emails = [];
    for(let i = 0; i < a.length; i++) {
        let e = a[i];
        if (e.href && e.href.startsWith('mailto:')) {
            let email = e.href.match(/([a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.[a-zA-Z0-9_-]+)/gi);
            if (email.length > 0 && emails.indexOf(email[0]) == -1) {
                emails.push(email[0]);
            }
        }
    }
    if (emails.length > 0) {
        let blob = new Blob([emails.join("\r\n")], { type: "text/plain;charset=utf-8"});
        saveBlob(blob, 'emails.txt');
    } else {
        alert('no mailto addresses');
    }
})();