Skip to search.
New User?
Register
Sign In
Help
Make Y! My Homepage
Mail
My Y!
Yahoo!
Yahoo! Help
Search
Search Web
Yahoo! Postmaster Help Topics
Tutorials
Contact Us
Hi there! Find your answer now.
Yahoo! Postmaster Help Topics
Basics
SMTP Error Codes
Complaint Feedback Loop
Top Questions
421 4.7.0 (TS01) Messages from x.x.x.x temporarily deferred due to user complaints - 4.16.55
554 Message type not allowed. UP Email not accepted for policy reasons
451 VS* Excessive unknown recipients - possible Open Relay
What are some best practices when sending to Yahoo! Mail?
421 4.7.1 (TS03) All messages from x.x.x.x permanently deferred
421 4.7.0 (TS02) Messages from x.x.x.x temporarily deferred due to user complaints - 4.16.56
My Help
Forgot your ID or password?
Sign In
Sign in to see your account information saved articles and more.
Recent Searches (
0
)
No recent searches
Clear all
Recently Viewed (
0
)
No Recently Viewed Articles
Clear all
Related Links
Yahoo! Universal Spam Policy
The Spamhaus Project
DKIM Resource