PHP Email Form Issue: Cannot POST - php

Question

I've been working on getting a PHP email form set up on my personal webpage, and I am running into an issue where when I hit submit, the page displays "Cannot post /mail.php".
I've seen several similar questions on this site before, but I haven't found any approaches that have solved the issue. I am new to PHP so I'm not sure how deep the error could be, or if I'm possibly missing something obvious.
I'm using Brackets Live Preview on Mac OS Big Sur.
Things I've tried:
Made sure that the mail.php file is in the same directory as my HTML files
Made sure I'm setting the name attribute in my HTML file so the PHP can pick up on the relevant entered information
Switched POST with GET (POST errors, GET download the PHP file instead of running it)
Downloaded PHP with Homebrew
Redownloaded Brackets
For reference this is my code:
HTML File:
<form action="mail.php" method="post">
<p>Name</p> <input type="text" name="name">
<p>Email</p> <input type="text" name="email">
<p>Message</p><textarea name="message" rows="6" cols="40"></textarea><br>
<input type="submit" value="Send"><input type="reset" value="Clear">
</form>
PHP File:
<?php
$name = $_POST['name'];
$email = $_POST['email'];
$message = $_POST['message'];
$formcontent="From $name \n Message: $message";
$recipient = "email.redacted#gmail.com";
$subject = "Contact Form";
$mailheader = "From $email \r\n";
mail($recipient, $subject, $formcontent, $mailheader) or die("Error");
?>
Any insight into what may be going wrong or some debugging steps to take would be much appreciated!

Answer 1

Here <? php you have whitespace after the ?. Remove it, and see what happens.
It should be <?php to be valid syntax. Otherwise the script breaks.
Edit: I'm not claiming this will solve any logical errors in your code, but that space in there is making the script not even PHP.

Answer 2

Is your form you have method="get". For you to access the information using $_POST you'll need to change it to method="post".
<form action="/mail.php" method="post">
<p>Name</p> <input type="text" name="name">
<p>Email</p> <input type="text" name="email">
<p>Message</p><textarea name="message" rows="6" cols="40"></textarea><br>
<input type="submit" value="Send"><input type="reset" value="Clear">
</form>
With regards to why your Bracket Live Preview is downloading the PHP file instead of running it. It sounds like your Bracket Live Preview isn't configured correctly.
You might be able to get some help from this question.
Using Brackets for PHP files