The Problem:
You’re attempting to send emails via Mailgun using RestClient in your Rails application, but receive a 400 Bad Request error with the message “‘from’ parameter is missing”. Your curl command works correctly, but your RestClient implementation fails. The discrepancy lies in how you’re supplying the email parameters to the RestClient::Request.execute method.
Understanding the “Why” (The Root Cause):
The curl command uses the -F flag, which signifies form data. This method implicitly constructs a multipart/form-data POST request. However, RestClient doesn’t automatically interpret parameters passed directly as form data. Instead, it treats them as request configuration options unless explicitly placed within the :payload hash. This is why Mailgun, expecting properly formatted form data, reports that the from parameter is missing because it’s not being correctly transmitted in the request body.
Step-by-Step Guide:
Step 1: Correct the RestClient Payload:
The core solution is to encapsulate all your email parameters within the :payload hash. This ensures that RestClient correctly sends them as form data in the POST request to the Mailgun API.
Replace your current RestClient code with the following:
RestClient::Request.execute(
:url => "https://api:[email protected]/v2/sandbox30000.mailgun.org/messages", #Fixed Sandbox Domain
:method => :post,
:payload => {
:from => 'Mailgun Sandbox <[email protected]>',
:to => '[email protected]',
:subject => 'Hello XYZ',
:text => 'Text body',
"h:X-My-Header" => 'www/mailgun-email-send'
},
:verify_ssl => false
)
Step 2: Verify Sandbox Domain Consistency:
Double-check that the sandbox domain (sandbox30000.mailgun.org in this example) used in your RestClient code matches the domain in your curl command and your actual Mailgun sandbox settings. Inconsistencies here are a common source of errors.
Step 3: Handle SSL Verification (Optional but Recommended):
While setting :verify_ssl => false might work, it’s generally not recommended for production environments. Consider setting up proper SSL certificate verification to enhance security. You can typically do this by installing the necessary CA certificates or configuring your system’s SSL settings.
Common Pitfalls & What to Check Next:
- API Key: Ensure your API key (
key-XYZ) is correct. A simple typo can prevent the request from succeeding.
- Mailgun Sandbox Limits: Check your Mailgun sandbox’s sending limits. If you’ve exceeded them, you might encounter this error.
- Network Connectivity: Confirm that your application has proper network access to the Mailgun API. Firewalls or network restrictions could interfere.
- Rate Limiting: If you are sending a large number of emails, Mailgun might be rate-limiting your requests. Look for rate limit information in the Mailgun API documentation and in any error messages you receive.
Still running into issues? Share your (sanitized) config files, the exact command you ran, and any other relevant details. The community is here to help!