What could be causing emails sent through a PHP mail system to not reach providers like web.de?

The emails sent through a PHP mail system may not be reaching providers like web.de due to issues with the server configuration, spam filters blocking the emails, or incorrect email headers. To solve this issue, ensure that the server is properly configured for sending emails, check for any spam filter restrictions, and make sure the email headers are correctly formatted. 

// Example PHP code snippet to set proper email headers
$to = "recipient@example.com";
$subject = "Test Email";
$message = "This is a test email.";
$headers = "From: sender@example.com\r\n";
$headers .= "Reply-To: sender@example.com\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-type: text/html; charset=iso-8859-1\r\n";

// Send email
$mail_sent = mail($to, $subject, $message, $headers);

if($mail_sent) {
    echo "Email sent successfully.";
} else {
    echo "Failed to send email.";
}

Keywords

PHP mail system email delivery web.de SMTP spam filters

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