// 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
11 guides · tag Headers
| Problem | In short | Tags | |
|---|---|---|---|
| Add a List-Unsubscribe header (one-click unsubscribe) | The List-Unsubscribe header lets Gmail, Yahoo and Outlook show an Unsubscribe button next to your sender name. Bulk senders must offer it in one click. | Fix it | |
| Email forwarding breaks SPF: how DKIM and ARC help | When someone forwards your email automatically, SPF fails because the forwarding server is not yours. A valid DKIM signature, and ARC on the forwarder, keep it trusted. | Fix it | |
| Contact form emails sent "From" the visitor's address | A website form that puts the visitor's email in the From field fails SPF and DMARC. Send from your own address and put the visitor in Reply-To instead. | Fix it | |
| Missing or wrong Date and Message-ID headers | Every email should carry a correct Date and a unique Message-ID. Without them, spam filters add points and Gmail can refuse the email. | Fix it | |
| Mailing lists and Google Groups break DMARC | When a discussion list re-sends your email, it changes it and sends it from its own servers, so DMARC can fail. Here is why, and what list owners and senders can do. | Fix it | |
| Choose a good sender name and From address | The sender name and address are the first things people see. Pick ones that are clear, stable and on your own domain, and readers trust and open your emails. | Fix it | |
| Garbled characters: fix encoding and charset problems (UTF-8) | Accents turning into "é" or question marks mean the email does not declare its text encoding correctly. Use UTF-8 everywhere and declare it. | Fix it | |
| Return-Path, envelope sender and From: why they must match your domain | An email has two sender addresses: the visible From and a hidden one used for bounces. For DMARC, at least SPF or DKIM must pass for the From domain. | Fix it | |
| Read email headers yourself: Authentication-Results, Received and DKIM-Signature | Headers are the hidden lines at the top of every email. Learn to find the three that explain why a message passed or failed. | Fix it | |
| Gmail "550-5.7.1 ... is not RFC 5322 compliant": fix missing or duplicate headers | Gmail rejected your email because its headers break the RFC 5322 standard: missing or duplicate From, Date or Message-ID. Here is how to fix it. | Fix it | |
| "450 4.1.8 Sender address rejected: Domain not found" / "553 5.1.8 Domain of sender address does not exist": fix | The receiver could not find your sender domain in DNS. Usually a typo, a local domain like .local, or a domain with no A or MX record. | Fix it |
Not sure what is wrong?
Send a test email or scan your domain: the report tells you which problem you have.