How important is it to follow RFC guidelines when sending emails through PHP scripts?

It is crucial to follow RFC guidelines when sending emails through PHP scripts to ensure that the emails are properly formatted and delivered successfully. Failure to adhere to these guidelines may result in emails being flagged as spam or not being delivered at all. 

// Example of sending an email with proper RFC guidelines
$to = 'recipient@example.com';
$subject = 'Test Email';
$message = 'This is a test email.';
$headers = 'From: sender@example.com' . "\r\n" .
    'Reply-To: sender@example.com' . "\r\n" .
    'X-Mailer: PHP/' . phpversion();

mail($to, $subject, $message, $headers);

Keywords

RFC guidelines email sending PHP scripts SMTP email validation

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