// 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
11 guides · tag Mailing list
| Problem | In short | Tags | |
|---|---|---|---|
| High bounce rate: clean your mailing list | Sending to addresses that no longer exist damages your reputation fast. Learn the difference between hard and soft bounces and remove bad addresses after every send. | 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. | Fix it | |
| Use a subdomain for marketing emails | Sending newsletters from a subdomain such as news.yourdomain.com keeps their reputation apart from your everyday business emails. Here is how to set it up. | Fix it | |
| Too many people mark your emails as spam | A high spam complaint rate sends all your emails to junk. Learn how to measure complaints, get feedback loops and send only to people who want your emails. | Fix it | |
| Use double opt-in for your newsletter | Ask every new subscriber to confirm their address with one click. Your list stays clean, bounces and complaints drop, and your emails reach the inbox more often. | Fix it | |
| Keep transactional and marketing emails apart | Receipts and password resets should never suffer because a newsletter got complaints. Send each kind of email through its own provider, stream or subdomain. | 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 | |
| Inactive subscribers hurt your reputation: re-engage or remove them | People who never open your emails drag down your reputation and can hide spam traps. Try to win them back once, then stop emailing those who stay silent. | Fix it | |
| Legal footer: unsubscribe link and postal address in marketing emails | Marketing emails need a clear way to unsubscribe and information about who you are. Here are the basics of CAN-SPAM and GDPR, and a simple footer to copy. | Fix it | |
| Bounce "550 5.1.1": the address does not exist | The receiving server says the mailbox does not exist. Check the spelling, remove the address from your lists, and keep your bounce rate low. | Fix it | |
| Bounce "552 5.2.2": the mailbox is full | The recipient has run out of storage space. It is their problem, not yours, but repeated "mailbox full" bounces often mean an abandoned address. | Fix it |
Not sure what is wrong?
Send a test email or scan your domain: the report tells you which problem you have.