我在000webhost上做了以下工作:

$headers  = "MIME-Version: 1.0" . "\r\n";
$headers .= "Content-type: text/html; charset=iso-8859-1" . "\r\n";
$headers .= "From: ". $from. "\r\n";
$headers .= "Reply-To: ". $from. "\r\n";
$headers .= "X-Mailer: PHP/" . phpversion();
$headers .= "X-Priority: 1" . "\r\n";

发送邮件时直接输入邮箱地址:

mail('email@gmail.com', $subject, $message, $headers)

使用“and not”。

这个代码工作，但电子邮件收到了半小时的延迟。

试试这个

if ($_POST['submit']) {
    $success= mail($to, $subject, $body, $from);
    if($success)
    { 
        echo '
        <p>Your message has been sent!</p>
        ';
    } else { 
        echo '
        <p>Something went wrong, go back and try again!</p>
        '; 
    }
}

可能问题出在邮件服务器的配置上。为了避免这类问题，或者您不必担心邮件服务器的问题，我建议您使用PHPMailer。

它是一个插件，拥有发送邮件所需的一切，唯一需要考虑的是启用SMTP端口(端口:25和465)。

require_once 'PHPMailer/PHPMailer.php';
require_once '/servicios/PHPMailer/SMTP.php';
require_once '/servicios/PHPMailer/Exception.php';

$mail = new \PHPMailer\PHPMailer\PHPMailer(true);
try {
    //Server settings
    $mail->SMTPDebug = 0;
    $mail->isSMTP();
    $mail->Host = 'smtp.gmail.com';
    $mail->SMTPAuth = true;
    $mail->Username = 'correo@gmail.com';
    $mail->Password = 'contrasenia';
    $mail->SMTPSecure = 'ssl';
    $mail->Port = 465;

    // Recipients
    $mail->setFrom('correo@gmail.com', 'my name');
    $mail->addAddress('destination@correo.com');

    // Attachments
    $mail->addAttachment('optional file');         // Add files, is optional

    // Content
    $mail->isHTML(true);// Set email format to HTML
    $mail->Subject = utf8_decode("subject");
    $mail->Body    = utf8_decode("mail content");
    $mail->AltBody = '';
    $mail->send();
}
catch (Exception $e) {
    $error = $mail->ErrorInfo;
}

把这两件事分开和一起尝试:

删除if($_POST['submit']){} 移除$from(只是我的直觉)

如果只使用mail()函数，则需要完成配置文件。

您需要打开邮件扩展，并设置SMTP smtp_port等，最重要的是，设置您的用户名和密码。没有它，邮件就无法发送。此外，您还可以使用PHPMail类来发送。

你可以使用PHPMailer，它工作得很完美，这里有一个代码示例:

<?php
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

require 'vendor/phpmailer/phpmailer/src/Exception.php';
require 'vendor/phpmailer/phpmailer/src/PHPMailer.php';
require 'vendor/phpmailer/phpmailer/src/SMTP.php';
$editor = $_POST["editor"];
$subject = $_POST["subject"];
$to = $_POST["to"];

try {

    if ($_SERVER["REQUEST_METHOD"] == "POST") {

        $mail = new PHPMailer();
        $mail->IsSMTP();
        $mail->Mailer = "smtp";
        $mail->SMTPDebug  = 1;
        $mail->SMTPAuth   = TRUE;
        $mail->SMTPSecure = "tls";
        $mail->Port       = 587;
        $mail->Host       = "smtp.gmail.com";//using smtp server
        $mail->Username   = "XXXXXXXXXX@gmail.com";//the email which will send the email 
        $mail->Password   = "XXXXXXXXXX";//the password

        $mail->IsHTML(true);
        $mail->AddAddress($to, "recipient-name");
        $mail->SetFrom("XXXXXXXXXX@gmail.com", "from-name");
        $mail->AddReplyTo("XXXXXXXXXX@gmail.com", "reply-to-name");
        $mail->Subject = $subject;
        $mail->MsgHTML($editor);




        if (!$mail->Send()) {
            echo "Error while sending Email.";
            var_dump($mail);
        } else {
            echo "Email sent successfully";
        }
    }
} catch (Exception $e) {
    echo $e->getMessage();
}