// 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 40
DNS 36
DMARC 33
Reputation 33
SPF 30
DKIM 27
Gmail 19
Security 19
Blacklist 18
Content 14
Headers 11
Mailing list 11
Spam score 11
Reverse DNS 10
Microsoft 365 8
Outlook 8
Mail server 7
MX 5
Yahoo 4
TLS 3
Apple 2
Google Workspace 2
BIMI 1
E-commerce 1
GMX 1
WordPress 1
Zoho 1
7 guides · tag Mail server
| Problem | In short | Tags | |
|---|---|---|---|
| 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 | |
| Your mail server is an open relay | An open relay lets anyone on the internet send email through your server. Spammers find it within hours and your IP ends up blacklisted. | Fix it | |
| "554 5.7.1 Relay access denied" when sending | Your mail server refuses to pass your email on because you are not logged in. Usually a missing SMTP login or the wrong port in your app or printer. | Fix it | |
| "450 4.7.1 Client host rejected: cannot find your hostname" (or "reverse hostname"): how to fix it | The receiving server could not match your IP to a hostname. Fix the reverse DNS (PTR) and its matching A record to stop this bounce. | Fix it | |
| "530 5.7.0 Must issue a STARTTLS command first" (and "451 5.7.3 STARTTLS is required"): how to fix it | The server requires an encrypted connection before it accepts your email. Turn on TLS in your app, printer or server and use the right port. | Fix it | |
| "4.4.7 Message expired" and "Delivery Status Notification (Delay)" ("451 4.4.0 DNS query failed"): causes and fixes | Your server tried to deliver for hours or days, then gave up. Why emails get delayed and expire, and how to find and fix the cause. | Fix it |
Not sure what is wrong?
Send a test email or scan your domain: the report tells you which problem you have.