Inserting E-mail Into DB - php

Question

Trying to build an email list in a database. I made this code, but it's not working and i'm not getting any errors. Am I on the right track?
HTML:
<div id="signup">
<h1>Sign-Up For Our Newsletter!</h1>
<form method="post" action="scripts/php/addSubscription.php">
<label for="email">E-mail: </label><input type="email" name="email" size="75"> <input type="submit">
</form>
</div>
PHP:
require('settings/globalVariables.php');
require('settings/mysqli_connect.php');
mysqli_select_db($conn,"newsletterlist");
$email = mysqli_real_escape_string($conn, $_POST['email']);
$sql = "INSERT INTO newsletterusers (email) VALUES ($email)";
if (mysqli_query($conn, $sql)) {
echo 'You have successfully subscribed!';
}
else {
echo 'Sorry, An error occured. Please try again.';
}
mysqli_close($conn);
$conn is a variable in mysqli_connect.php
Adding contents of mysqli_connect.php just for reference:
<?php
$conn = mysqli_connect(DB_HOST, DB_USER, DB_PASS);
?>
I use this on several databases and it connects each time.
EDIT:
Updated code per answers/comments and still nothing is happening.
require('settings/globalVariables.php');
require('settings/mysqli_connect.php');
mysqli_select_db($conn,"newsletterlist");
$email = mysqli_real_escape_string($conn, $_POST['email']);
$sql = "INSERT INTO newsletterusers (email) VALUES ('$email')";
if (mysqli_query($conn, $sql)) {
echo 'You have successfully subscribed!';
}
else {
echo "Error: ".mysqli_error($conn);
}
mysqli_close($conn);
SOLVED:
require('/home/jollyrogerpcs/public_html/settings/globalVariables.php');
require('/home/jollyrogerpcs/public_html/settings/mysqli_connect.php');
mysqli_select_db($conn,"newsletterlist");
$email = mysqli_real_escape_string($conn, $_POST['email']);
$sql = "INSERT INTO newsletterusers (email) VALUES ('$email')";
if (mysqli_query($conn, $sql)) {
echo 'You have successfully subscribed!';
}
else {
echo "Error: ".mysqli_error($conn);
}
mysqli_close($conn);

Answer 1

You are currently getting an error but your code doesn't show you. Print the error for a start:
if (mysqli_query($conn, $sql)) {
echo 'You have successfully subscribed!';
}
else {
echo "Error: ".mysqli_error($conn);
}
The real error you are getting is a syntax error. This is how your generated SQL looks like:
INSERT INTO newsletterusers (email) VALUES (hello#email.com)
Note that there are no quotes around it, you can fix it by surrounding $email with quotes:
$sql = "INSERT INTO newsletterusers (email) VALUES ('$email')";