diff --git a/admin.php b/admin.php
index 4816f53..106bd40 100644
--- a/admin.php
+++ b/admin.php
@@ -357,16 +357,27 @@ function fb_admin_save_settings() {
     $sp = (string)(isset($_POST['smtp_pass']) ? $_POST['smtp_pass'] : '');
     if (trim($sp) !== '') { fb_set_setting('smtp.pass', $sp); }
 
-    $smtpPort = (int)$post('smtp.port', 465);
-    if ($smtpPort <= 0 || $smtpPort > 65535) { $smtpPort = 465; }
-    fb_set_setting('smtp.port', $smtpPort);
+    // 端口留空 = 用默认 465。删键回落，不要存成 0（0 端口根本连不上）
+    $portRaw = trim((string)$post('smtp.port', ''));
+    if ($portRaw === '') {
+        fb_unset_setting('smtp.port');
+    } else {
+        $smtpPort = (int)$portRaw;
+        if ($smtpPort <= 0 || $smtpPort > 65535) { $smtpPort = 465; }
+        fb_set_setting('smtp.port', $smtpPort);
+    }
 
     $sec = strtolower(trim((string)$post('smtp.secure', 'ssl')));
     if (!in_array($sec, ['ssl', 'tls', ''], true)) { $sec = 'ssl'; }
     fb_set_setting('smtp.secure', $sec);
 
-    $smtpTo = (int)$post('smtp.timeout', 15);
-    fb_set_setting('smtp.timeout', max(5, min(60, $smtpTo)));
+    // 超时留空 = 用默认 15
+    $tmoRaw = trim((string)$post('smtp.timeout', ''));
+    if ($tmoRaw === '') {
+        fb_unset_setting('smtp.timeout');
+    } else {
+        fb_set_setting('smtp.timeout', max(5, min(60, (int)$tmoRaw)));
+    }
     fb_set_setting('smtp.verify_ssl', (int)(bool)$post('smtp.verify_ssl'));
 
     // 没填 from 时用 user 兜底（绝大多数 SMTP 要求两者一致）
@@ -387,8 +398,14 @@ function fb_admin_save_settings() {
     fb_set_setting('notify.enabled',        (int)(bool)$post('notify.enabled'));
     fb_set_setting('notify.on_every_reply', (int)(bool)$post('notify.on_every_reply'));
     fb_set_setting('notify.admin_new_thread', (int)(bool)$post('notify.admin_new_thread'));
-    $cd = (int)$post('notify.cooldown_seconds', 60);
-    fb_set_setting('notify.cooldown_seconds', max(0, min(86400, $cd)));
+    // 冷却秒数留空 = 用默认 300（config 里的出厂值）。注意 0 是合法值（表示不限制），
+    // 所以要用「空串」而不是「0」来区分"没填"和"填了 0"
+    $cdRaw = trim((string)$post('notify.cooldown_seconds', ''));
+    if ($cdRaw === '') {
+        fb_unset_setting('notify.cooldown_seconds');
+    } else {
+        fb_set_setting('notify.cooldown_seconds', max(0, min(86400, (int)$cdRaw)));
+    }
 
     fb_set_setting('moderation.enabled', $post('moderation.enabled') ? 1 : 0);
 
@@ -937,12 +954,19 @@ fb_layout_head('管理后台', ['robots' => 'noindex,nofollow']);
     <input type="hidden" name="act" value="settings">
     <h2 style="margin:24px 0 10px">邮件通知</h2>
     <?php
+      // ⚠️ config.example.php 的 smtp 段有全套出厂示例值
+      // （smtp.example.com / noreply@example.com / 轻反馈 …），
+      // fb_cfg() 合并后表单会把这些当成"已填内容"显示出来，
+      // 用户点进去得先删一遍。所以回显一律过 fb_form_val()：
+      // 数据库里没设过 = 没自定义 = 显示空，示例只留在 placeholder。
       $smOn    = (bool)fb_cfg('smtp.enabled', false);
-      $smHost  = (string)fb_cfg('smtp.host', '');
-      $smUser  = (string)fb_cfg('smtp.user', '');
-      $smFrom  = (string)fb_cfg('smtp.from', '');
-      $smName  = (string)fb_cfg('smtp.from_name', '');
-      $smPort  = (int)fb_cfg('smtp.port', 465);
+      $smHost  = fb_form_val(fb_cfg('smtp.host', ''), 'smtp.example.com', 'smtp.host');
+      $smUser  = fb_form_val(fb_cfg('smtp.user', ''), 'noreply@example.com', 'smtp.user');
+      $smFrom  = fb_form_val(fb_cfg('smtp.from', ''), 'noreply@example.com', 'smtp.from');
+      $smName  = fb_form_val(fb_cfg('smtp.from_name', ''), '轻反馈', 'smtp.from_name');
+      // 端口出厂 465，没设过就留空让 placeholder 提示，别预填数字
+      $smPortRaw = fb_form_val((string)(int)fb_cfg('smtp.port', 465), '465', 'smtp.port');
+      $smPort    = $smPortRaw === '' ? '' : (string)(int)$smPortRaw;
       $smSec   = (string)fb_cfg('smtp.secure', 'ssl');
       $smHasPw = (string)fb_cfg('smtp.pass', '') !== '';
       $smTmo   = (int)fb_cfg('smtp.timeout', 15);
@@ -959,7 +983,8 @@ fb_layout_head('管理后台', ['robots' => 'noindex,nofollow']);
       <label class="field"><span>端口与加密</span>
         <div style="display:flex;gap:8px">
           <input type="number" name="smtp_port" min="1" max="65535" style="flex:0 0 110px"
-                 value="<?php echo (int)$smPort; ?>">
+                 placeholder="465"
+                 value="<?php echo e($smPort); ?>">
           <select name="smtp_secure" style="flex:1">
             <option value="ssl"<?php echo $smSec === 'ssl' ? ' selected' : ''; ?>>SSL（通常 465）</option>
             <option value="tls"<?php echo $smSec === 'tls' ? ' selected' : ''; ?>>STARTTLS（通常 587）</option>
@@ -991,7 +1016,8 @@ fb_layout_head('管理后台', ['robots' => 'noindex,nofollow']);
       <summary style="cursor:pointer;font-size:13px;color:var(--muted)">高级选项</summary>
       <div class="grid2" style="margin-top:8px">
         <label class="field"><span>超时（秒）</span>
-          <input type="number" name="smtp_timeout" min="5" max="60" value="<?php echo (int)$smTmo; ?>"></label>
+          <input type="number" name="smtp_timeout" min="5" max="60" placeholder="15"
+                 value="<?php echo e(fb_form_val((string)(int)$smTmo, '15', 'smtp.timeout')); ?>"></label>
         <label class="check" style="align-self:end"><input type="checkbox" name="smtp_verify_ssl" value="1"<?php echo $smVerify ? ' checked' : ''; ?>> 校验服务器 SSL 证书
           <span class="hint" style="display:block;margin-left:24px">服务器缺 CA 证书时可临时取消，但不建议。</span></label>
       </div>
@@ -1013,8 +1039,9 @@ fb_layout_head('管理后台', ['robots' => 'noindex,nofollow']);
     <label class="check"><input type="checkbox" name="notify_admin_new_thread" value="1"<?php echo fb_cfg('notify.admin_new_thread', false) ? ' checked' : ''; ?>> 有新反馈时通知管理员
       <span class="hint" style="display:block;margin-left:24px">发到「站点信息」里填的官方邮箱。</span></label>
     <label class="field" style="max-width:280px"><span>同一帖同一收件人的最短发信间隔（秒）</span>
-      <input type="number" name="notify_cooldown_seconds" min="0" max="86400"
-             value="<?php echo (int)fb_cfg('notify.cooldown_seconds', 60); ?>">
+      <?php /* 出厂默认是 300（见 config.example.php 的 notify.cooldown_seconds） */ ?>
+      <input type="number" name="notify_cooldown_seconds" min="0" max="86400" placeholder="300"
+             value="<?php echo e(fb_form_val((string)(int)fb_cfg('notify.cooldown_seconds', 300), '300', 'notify.cooldown_seconds')); ?>">
       <i class="hint">0 = 不限制。</i></label>
     <div class="form-actions">
       <button class="btn primary" type="submit">保存邮件设置</button>