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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

13 guides · tag Blacklist

Problem	In short	Tags
Your sending IP address is on a blacklist	A blacklist is a public list of IP addresses known for sending spam. Find out if the IP is yours, fix the cause, then ask for removal.	Blacklist Security	Fix it
Your domain is on a blacklist (Spamhaus DBL, SURBL, URIBL)	Domain blacklists list domain names seen in spam. They follow your domain wherever you send from. Find the cause, clean up, then request removal.	Blacklist Security	Fix it
Bounce "550 5.7.1": message rejected or blocked by policy	A 5.7.1 bounce means the receiving server refused your email on purpose. Learn to read bounce messages, find the real reason and fix it.	Bounce Blacklist Reputation	Fix it
Warm up a new domain or IP address	A new domain or IP has no reputation yet. Sending a large campaign on day one looks like spam. Start small and increase your volume step by step.	Reputation Blacklist	Fix it
Links that hurt deliverability	URL shorteners, link text that shows one address but points to another, and links to blacklisted domains are classic spam signs. Use plain links to your own domain.	Content Blacklist Spam score	Fix it
Spam traps and bought email lists	Spam traps are hidden addresses that catch senders with bad lists. Hitting them can blacklist you. Never buy lists, and only email people who asked for it.	Mailing list Reputation Blacklist	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.	Mail server Security Blacklist	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.	Reputation Reverse DNS Blacklist Bounce	Fix it
Your emails are not received at all: a step-by-step checklist	Your recipients say nothing arrived, not even in spam. Follow these steps in order to find where the email gets lost.	Bounce DNS Blacklist	Fix it
Shared IP address with a bad reputation	You send from an IP address used by other customers, and one of them is spamming. Your emails pay the price. Here is how to tell and what to ask your provider.	Blacklist Reputation	Fix it
A hacked email account is sending spam: what to do	Someone has your password and is sending spam from your mailbox. Lock them out, remove what they left behind, then repair your reputation.	Security Blacklist Reputation	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.	Blacklist Reputation Reverse DNS	Fix it
Use a custom tracking domain for links in your emails	Newsletter tools rewrite your links through a shared tracking domain. If that domain gets a bad name, your emails suffer. Use your own instead.	Content Reputation Blacklist DNS	Fix it

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