和我的邮件服务器有什么关系吗？如何防止我的电子邮件被视为垃圾邮件？我的电子邮件内容需要链接:)

PHP代码：

// Send Email to the user
$headers =  'MIME-Version: 1.0' . "\r\n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";
$headers .= 'From: user@domain.com' . "\r\n";

// Email Variables

$toUser  = 'touser@other.com'; // recipient
$subject = "Subject HERE!!"; // subject
$body    = '<div style="font-family:Arial; color:#333;">
                Some content here ...
        <a href="www.google.com" target="_blank"> Link here</a> 
        </div>';

if(mail($toUser,$subject,$body,$headers)){
    echo "Email SENT" . '<br>';
} else {
    echo "Email cannot sent" . '<br>';
};