// how to fix
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.
DNS 33
DMARC 28
SPF 28
DKIM 26
Reputation 24
Bounce 16
Security 16
Blacklist 13
Gmail 13
Content 12
Mailing list 11
Spam score 10
Headers 9
Reverse DNS 7
Mail server 4
Microsoft 365 4
MX 4
Outlook 4
TLS 2
Apple 1
BIMI 1
E-commerce 1
Google Workspace 1
WordPress 1
Yahoo 1
Zoho 1
7 guides · tag Reverse DNS
| Problem | In short | Tags | |
|---|---|---|---|
| No reverse DNS (PTR), or it does not match | Reverse DNS gives a name to your server's IP address. Without it, or if it does not point back, your server looks like an infected home computer. | Fix it | |
| Invalid HELO/EHLO hostname | Your server introduces itself with a name that is not valid, such as localhost or a bare IP. Spam filters distrust this. Give it a real name that matches reverse DNS. | Fix it | |
| Running your own mail server: the deliverability checklist | A self-hosted Postfix server can deliver well, but only if every basic is right: reverse DNS, SPF, DKIM, DMARC, TLS and no open relay. | Fix it | |
| How to set reverse DNS (PTR) at your hosting company | The PTR record of your server IP is set by your hosting company, not in your domain DNS. Here are the general steps at OVH, Hetzner, Scaleway, AWS and DigitalOcean. | Fix it | |
| Emails blocked by Orange, SFR, Free or other French ISPs | French internet providers filter strictly with their own rules. Fix your reverse DNS and authentication, slow down, and use their contact procedures. | Fix it | |
| Your IP is on the Barracuda blacklist (BRBL) | Barracuda devices block emails from IPs on its reputation list. Find out why you were listed, fix the cause, then ask for removal for free. | Fix it | |
| Gmail bounce "550 5.7.25": reverse DNS (PTR) required | Gmail refuses your email because your sending IP has no reverse DNS, or one that does not point back to the IP. Ask your host to set a proper PTR. | Fix it |
Not sure what is wrong?
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