PHP7.1.9+Mailgun环境下curl_exec返回消息但邮件未发送问题

Hey David, let's break down why your emails aren't hitting the inbox even though curl_exec is returning a response. I've worked through similar Mailgun issues before, so here are the key steps to diagnose and fix this:

1. First, Capture and Inspect the Full Mailgun Response #

Right now, you're not checking what exactly Mailgun is sending back. Even if curl_exec returns something, it could be an error message that tells you exactly what's wrong. Update your code to log/print the response and HTTP status code:

function send_email($from, $to, $subject, $body) {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
    curl_setopt($ch, CURLOPT_USERPWD, 'api:your-actual-private-api-key'); // Replace with real key
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'POST');
    curl_setopt($ch, CURLOPT_URL, 'https://api.mailgun.net/v3/your-sandbox-domain.mailgun.org/messages'); // Replace with real URL

    // Critical missing piece: Pass your email content as POST fields
    curl_setopt($ch, CURLOPT_POSTFIELDS, array(
        'from'    => $from,
        'to'      => $to,
        'subject' => $subject,
        'text'    => $body // Use 'html' instead of 'text' if sending HTML content
    ));

    $response = curl_exec($ch);
    $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE); // Grab HTTP status code
    curl_close($ch);

    // Print these to debug
    var_dump(json_decode($response, true)); // Decode JSON response for readability
    echo "HTTP Status Code: " . $httpCode;

    return $response;
}

Mailgun returns detailed JSON errors (like invalid API keys, missing parameters, or unauthorized recipients) that will point you straight to the issue. For example, a 401 Unauthorized means your API key is wrong, and a 400 Bad Request usually means missing or invalid fields.

2. Verify Your API Key and Domain URL #

• API Key: Make sure you're using the Private API Key from Mailgun's dashboard (under Domains > Your Sandbox Domain > API Keys). Don't use the Public Key—this is a super common mistake.
• Domain URL: Your request URL must follow the format https://api.mailgun.net/v3/your-sandbox-domain.mailgun.org/messages. Double-check that you've replaced the placeholder with your actual sandbox domain (it looks like sandbox123abc.mailgun.org).

3. You Forgot to Pass Email Parameters in the POST Request! #

Looking at your original code, you never sent the $from, $to, $subject, or $body variables to Mailgun via POST fields. Without these, Mailgun has no idea what email to send—this is almost certainly a core issue. The code above adds CURLOPT_POSTFIELDS to fix this gap.

4. Check Sandbox Domain Restrictions #

Mailgun's sandbox domains only allow sending to pre-verified email addresses. If you're trying to send to an email that hasn't been added and verified in your Mailgun dashboard, the API will return an error (even if curl_exec returns a response). Head to your Mailgun domain settings and confirm the recipient is in your authorized list.

5. Ensure cURL is Configured Correctly #

• Make sure the cURL extension is enabled in your PHP 7.1.9 setup. You can check this by running phpinfo() and looking for the cURL section.
• Confirm cURL supports HTTPS (Mailgun requires HTTPS for API requests). Run var_dump(curl_version()) and check that the ssl_version field is present and not empty.

Once you add the response logging, you'll get a clear picture of what's failing. Start there—it's the fastest way to resolve the issue.

内容的提问来源于stack exchange，提问作者David