// 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
4 guides · tag Yahoo
| Problem | In short | Tags | |
|---|---|---|---|
| Yahoo and AOL "421 4.7.0 [TSS04]" deferrals | Yahoo is temporarily refusing your emails because of their volume or complaints. Slow down, keep retrying, and fix what Yahoo does not like. | Fix it | |
| Yahoo / AOL "553 5.7.1 [BL21] Connections will not be accepted ... Spamhaus's list" (BL23): how to fix it | Yahoo and AOL refuse your server because its IP is on a Spamhaus list. Find which list, fix the cause, get delisted and resend. | Fix it | |
| Yahoo "554 5.7.9 Message not accepted for policy reasons" and "[PH01]": causes and fixes | Yahoo refused your email for policy reasons: often failed DMARC or authentication, sometimes suspicious content. How to find the cause and fix it. | Fix it | |
| Yahoo "421 4.7.0 [TSS09] All messages from [IP] will be permanently deferred; Retrying will NOT succeed": what to do | Yahoo has stopped accepting mail from your IP because of poor reputation. Why TSS09 happens, how to recover and how to contact Yahoo. | Fix it |
Not sure what is wrong?
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