我无法以 html 形式发送从邮箱携带的电子邮件地址。当我用 someone@yahoo.com 填写表单邮箱时，电子邮件被发送到邮箱，但是当我用 someon@gmail.com 填写表单邮箱时，电子邮件脚本有效，但电子邮件没有进入邮箱或垃圾邮件文件夹。
-----*This is the html code*-------
<input type="email" name="email" id="email" size="70" /></td>
-----*-------------
$email_from = "$mail";
$email_to = "someone@gmail.com";
$email_message ="test message";
$email_subject = "Registration form "; // email subject line
$headers .= 'MIME-Version: 1.0'."\r\n";
$headers .= 'Content-type: text/html; charset=iso-8859-1'."\r\n";
$headers .= 'From:'.$mail;
mail($email_to, $email_subject, $email_message, $headers);