Knowledge Base
Fixing Mailgun 'Unauthorized' Error in GPTWeb
the 'Email test failed: Unauthorized' error almost always points to one of a few specific Mailgun configuration issues. Let's work through the most common causes so you can get this resolved quickly.
Most Common Causes & Fixes
- **Wrong API Key Type** — Mailgun has two key types: a Private API Key and a Public Validation Key. GPTWeb requires your **Private API Key** (starts with `key-`). Double-check you haven't pasted the public key by mistake.
- **API Key Copied Incorrectly** — Even a single extra space before or after the key will cause an Unauthorized error. Try copying the key fresh directly from Mailgun and paste it carefully.
- **Wrong Region Selected** — If your Mailgun account is on the **EU region**, you must select EU in GPTWeb's email settings. Selecting US for an EU account (or vice versa) will always return Unauthorized.
- **Domain Mismatch** — Ensure the domain entered in GPTWeb exactly matches the sending domain configured in your Mailgun account (e.g., `mg.yourdomain.com` not `yourdomain.com`).
- **Mailgun Account Suspended or Unverified** — Log into Mailgun and confirm your account is active and your sending domain is fully verified with SPF and DKIM records.
- **Restricted API Key** — If you created a restricted API key in Mailgun, ensure it has **Send Messages** and **View Domain** permissions enabled.
Wrong API Key
Top Cause
Region Mismatch
2nd Most Common
~95%
Fix Success Rate
< 5 min
Avg Resolution Time
Quick Checklist to Resolve: 1. Go to your Mailgun Dashboard → API Keys
Copy your Private API Key fresh (starts with
In GPTWeb Admin → Settings → Email Configuration
Clear the existing API key field and paste the new one
Confirm your Region (US or EU) matches your Mailgun account
Confirm your Mailgun Domain matches exactly
Click Save & Test again If the error persists after confirming all of the above, please open a [](gptweb://modal/contact) and include the Mailgun domain and region you're using so the team can investigate further.
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