Mailgun Setup Guide

Connect Mailgun to FormBlade for powerful email delivery with detailed analytics and routing rules.

Free tier details

Step 1: Create a Mailgun account

1. Go to signup.mailgun.com
2. Sign up with your email address
3. Confirm your email address via the verification link
4. Optional but recommended: Add a credit card under Billing to remove the 5-recipient restriction

Step 2: Add and verify a custom domain

Mailgun gives you a sandbox domain for testing, but it only sends to authorized recipients. For production use, you need to verify a custom domain.

1. In the Mailgun dashboard, go to Sending → Domains
2. Click Add New Domain
3. Enter a subdomain dedicated to sending (e.g., mail.yourdomain.com or mg.yourdomain.com). Using a subdomain is recommended so it does not interfere with your main domain's email
4. Mailgun will display DNS records you need to add:

Required DNS records

The exact record values are shown in the Mailgun dashboard after you add your domain. Add all records at your DNS provider, then:

1. Go back to Sending → Domains in Mailgun
2. Click Verify DNS Settings on your domain
3. Wait for the records to propagate (usually 5–30 minutes, can take up to 48 hours)
4. All three records should show green checkmarks when verified

Step 3: Get your API key

1. In the Mailgun dashboard, click your avatar in the top-right corner
2. Go to API Security (or navigate to app.mailgun.com/settings/api_security)
3. Your Private API Key is listed at the top (it starts with key-)
4. Click the eye icon to reveal it, then copy it

Step 4: Configure FormBlade

1. Log in to your FormBlade dashboard
2. Open the form you want to configure
3. Go to the Settings tab
4. Under Email Provider, select Mailgun
5. Paste your API key into the API Key field
6. Set your From Email to an address on your verified domain (e.g., forms@mg.yourdomain.com)
7. Optionally set a From Name
8. Click Save

Step 5: Send a test email

1. Click Send Test Email in the Email Provider section
2. Check your inbox for the test notification
3. If it fails, verify that your domain is verified, your API key is correct, and the recipient is not restricted by the 5-address limit

Troubleshooting

"Forbidden" or "401 Unauthorized" error

• Double-check the API key. Make sure you copied the Private API Key from API Security, not a domain verification code
• Check for extra spaces before or after the key

"Domain not found" error

• The "From Email" domain must match a verified domain in Mailgun
• If you verified mg.yourdomain.com, the from address must be on that exact subdomain (e.g., forms@mg.yourdomain.com), not the root domain

Emails only sending to some addresses

• If you do not have a credit card on file, Mailgun restricts sending to 5 whitelisted recipients
• Add a credit card at Billing → Payment Methods in the Mailgun dashboard to remove this restriction
• If you are still using the sandbox domain, switch to a verified custom domain

Emails going to spam

• Make sure all three DNS records (SPF, DKIM, MX) are verified. Missing records significantly hurt deliverability
• Use a subdomain for sending (e.g., mg.yourdomain.com) to protect your main domain's reputation
• Ensure the "From Email" domain matches your verified Mailgun domain

No delivery logs

• The free tier retains logs for only 1 day. If you need to investigate delivery issues, check within 24 hours of sending
• Paid plans offer up to 30 days of log retention

Mailgun free tier summary

• 100 emails/day — sufficient for low-traffic forms
• 5 recipients without credit card — the biggest catch. Add a credit card to remove this limit
• Custom domain required — sandbox domain is for testing only
• 1-day log retention — paid plans get longer retention
• DNS verification required — you must add SPF, DKIM, and MX records

For most users who want a free email solution, Brevo is a simpler choice with fewer restrictions. Mailgun shines on paid plans where you get access to advanced routing, analytics, and higher volume.

Common gotchas

• 5-recipient limit without a credit card — This is the biggest surprise for new Mailgun users. Without a credit card on file, you can only send emails to 5 manually whitelisted addresses. Add a credit card (you will not be charged unless you upgrade) to remove this restriction.
• Custom domain is required for production — The sandbox domain (sandboxXXXXX.mailgun.org) is for testing only and limited to authorized recipients. You must verify a custom domain to send to arbitrary recipients.
• Use a subdomain for sending — Always verify a subdomain like mg.yourdomain.com or mail.yourdomain.com rather than your root domain. This protects your main domain's sending reputation and avoids conflicts with existing email (MX records).
• Three DNS records required — Mailgun needs SPF (TXT), DKIM (TXT), and MX records. All three must be verified. The MX record is required even if you are only sending (not receiving) email through Mailgun.
• Private API key vs. domain sending keys — The Private API Key (found under API Security) works for all domains. Domain-specific sending keys (found on each domain's settings page) are scoped to that one domain and are more secure. Either will work with FormBlade.
• 1-day log retention on free tier — Free accounts only retain delivery logs for 24 hours. If you need to troubleshoot a delivery issue, check the logs within a day of sending.
• EU vs. US region — When creating your Mailgun account, you may be asked to choose a region (US or EU). This affects your API endpoint. Make sure your API calls go to the correct region. FormBlade handles this automatically based on your API key.

Quick reference: where to find things in Mailgun