質問者さんが使用しているvalidationEngineがjQuery-Validation-Engineならば、以下のように行ってはいかがでしょうか?
HTML
1<!DOCTYPE html>
2<html lang="ja">
3<head>
4 <meta charset="utf-8">
5 <title>タイトル</title>
6 <link rel="stylesheet"
7 href="https://cdnjs.cloudflare.com/ajax/libs/jQuery-Validation-Engine/2.6.4/validationEngine.jquery.min.css">
8 <style type="text/css">
9 * {
10 margin: 0;
11 padding: 0;
12 }
13 </style>
14</head>
15<body>
16<form action="page.php" method="post" id="form1" name="send">
17 <input type="hidden" name="UserID" value="hinata">
18 <input type="hidden" name="MagazineID" value="64">
19 <input type="hidden" name="HTMLMail" value="1">
20 <input type="hidden" name="MoreItem" value="1">
21 <div id="mailwrap">
22 <div id="address_area">
23 <p>
24 <label>お名前をご入力ください。
25 <input type="text" name="name" class="input1 validate[required]">
26 </label>
27 </p>
28 <p>
29 <label>メールアドレスをご入力ください。
30 <input type="email" name="email" class="input3 validate[required,custom[email]] mail-address">
31 </label>
32 </p>
33 </div><!-- end address_area -->
34 </div><!-- end meilma-wrap -->
35 <input type="image" alt="送信" src="image/btn.png" class="btn" id="send_button" disabled="disabled">
36</form>
37<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
38<script src="https://cdnjs.cloudflare.com/ajax/libs/jQuery-Validation-Engine/2.6.4/jquery.validationEngine.min.js"></script>
39<script src="https://cdnjs.cloudflare.com/ajax/libs/jQuery-Validation-Engine/2.6.4/languages/jquery.validationEngine-ja.min.js"></script>
40<script>
41 $(function () {
42 $("#form1").validationEngine("attach", {focusFirstField: false});
43
44 $("input").on("input", function () {
45 if ($("#form1").validationEngine("validate")) {
46 $("#send_button").prop("disabled", false);
47 } else {
48 $("#send_button").prop("disabled", true);
49 }
50 });
51
52 $("#send_button").on("click", function () {
53 if ($("#form1").validationEngine("validate")) {
54 $("#form1").submit();
55 }
56 });
57 });
58</script>
59</body>
60</html>
#追記
HTML
1<!DOCTYPE html>
2<html lang="ja">
3<head>
4 <meta charset="utf-8">
5 <title>タイトル</title>
6 <link rel="stylesheet"
7 href="https://cdnjs.cloudflare.com/ajax/libs/jQuery-Validation-Engine/2.6.4/validationEngine.jquery.min.css">
8 <style type="text/css">
9 * {
10 margin: 0;
11 padding: 0;
12 }
13 </style>
14</head>
15<body>
16<form action="page.php" method="post" id="form1" name="send">
17 <input type="hidden" name="UserID" value="hinata">
18 <input type="hidden" name="MagazineID" value="64">
19 <input type="hidden" name="HTMLMail" value="1">
20 <input type="hidden" name="MoreItem" value="1">
21 <div id="mailwrap">
22 <div id="address_area">
23 <p>
24 <label>お名前をご入力ください。
25 <input type="text" name="name" class="input1 validate[required]">
26 </label>
27 </p>
28 <p>
29 <label>メールアドレスをご入力ください。
30 <input type="email" name="email" class="input3 validate[required,custom[email]] mail-address">
31 </label>
32 </p>
33 </div><!-- end address_area -->
34 </div><!-- end meilma-wrap -->
35 <input type="image" alt="送信" src="" class="btn" id="send_button" disabled="disabled">
36</form>
37<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
38<script src="https://cdnjs.cloudflare.com/ajax/libs/jQuery-Validation-Engine/2.6.4/jquery.validationEngine.min.js"></script>
39<script src="https://cdnjs.cloudflare.com/ajax/libs/jQuery-Validation-Engine/2.6.4/languages/jquery.validationEngine-ja.min.js"></script>
40<script>
41 $(function () {
42 $("#form1").validationEngine("attach", {focusFirstField: false});
43
44 $("input").on("input", function () {
45 if ($("#form1").validationEngine("validate")) {
46 $("#send_button").prop({"disabled": false, "src": "image/btn.png"});
47 } else {
48 $("#send_button").prop({"disabled": true, "src": ""});
49 }
50 });
51
52 $("#send_button").on("click", function () {
53 if ($("#form1").validationEngine("validate")) {
54 $("#form1").submit();
55 }
56 });
57 });
58</script>
59</body>
60</html>