如何防止 Gmail 堆积成 "conversation" 通过 PHP mail() 发送的电子邮件?

How to prevent Gmail from stacking into a "conversation" emails sent via PHP mail()?

我有一个 Web 表单,它使用以下 PHP 代码发送电子邮件:

$senderEmail = "sender@sender.com"
$senderName = "John Smith"

$noreplyEmail = "noreply@receiver.com"
$receiverEmail = "inbox@receiver.com"

$header = "MIME-Version: 1.0\r\nContent-type: text/plain; charset=UTF-8\r\n";
$header .= 'From: "' . $senderName . '" <' . $noreplyEmail . ">\r\n";
$header .= 'Reply-To: "' . $senderName . '" <' . $senderEmail . ">";

$subject = "Contact form";
$message = "...";

mail($receiverEmail, $subject, $message, $header);

问题是,虽然每次 $senderName$senderEmail$message 在收件人的收件箱(这是一个 Gmail 域收件箱)中都不同,但电子邮件会堆积到Gmail 系统的对话。

防止这种堆叠并始终将它们作为单独的单独电子邮件接收的正确方法是什么?

简单:您必须更改电子邮件的 Subject

mail('hi@example.com', 'Test', 'Hi there 3')

mail('hi@example.com', 'Test 3', 'Hi there 3')

可能是 $subject = "Contact from" . $senderName;