// how to fix
Not sure what is wrong?How to fix email problems
Your test or scan found a problem? Find the matching guide below: what it means, why it matters, and how to fix it step by step.
Bounce 60
DNS 52
SPF 40
Reputation 39
DMARC 38
DKIM 34
Security 26
Gmail 21
Blacklist 18
Microsoft 365 17
Mailing list 16
Content 15
Mail server 13
Headers 12
Reverse DNS 12
SMTP 12
Spam score 12
Outlook 10
MX 9
Amazon SES 7
Google Workspace 5
TLS 5
Yahoo 5
Mailgun 4
Postmark 3
Apple 2
SendGrid 2
WordPress 2
Zoho 2
ARC 1
BIMI 1
Cloudflare 1
E-commerce 1
GMX 1
Resend 1
T-Online 1
4 guides · tag Mailgun
| Problem | In short | Tags | |
|---|---|---|---|
| Mailgun domain not verified: fix the SPF, DKIM, MX and CNAME records | Mailgun shows your domain as unverified or refuses to send from it. Add the right SPF and DKIM records, avoid common DNS mistakes and verify. | Fix it | |
| Mailgun "Sandbox subdomains are for test purposes only" (403): fix it | Mailgun refuses to send from your sandbox domain to an address that is not an authorized recipient. Authorize test addresses or add your own domain. | Fix it | |
| Mailgun "401 Forbidden": wrong API key or EU/US region mismatch | Mailgun returns 401 Forbidden or Unauthorized. Check the API key type, the "api" username and whether your domain uses the US or EU endpoint. | Fix it | |
| Mailgun 605 "Not delivering to previously bounced address": fix | Mailgun refuses to send with code 605 because the address bounced before. Learn when to remove it from the bounce list and when to leave it there. | Fix it |
Not sure what is wrong?
Send a test email or scan your domain: the report tells you which problem you have.