Yahoo! Mail rarely outright rejects mail upon connection. If this is happening to your email, here are the common error messages you should be seeing in your SMTP logs:

• 553 VS99-IP1 deferred - see related help topic

If you see this error message, please visit this page for assistance. or:

• 451 VS1-IP Excessive unknown recipients - possible Open Relay (#4.1.8)
• 451 VS1-MF Excessive unknown recipients - possible Open Relay (#4.4.5)

If you see any of these 2 error messages, please visit our deprioritization page for more information.

If you do not see error messages similar to the above, then your emails are neither being blocked nor deprioritized. Listed below are other possible error messages you may be seeing and the steps you should take to address them:

• 554 delivery error: dd This user doesn't have a yahoo.com account ({recipients'userid}@yahoo.com).

You should not retry the message and remove the email address from your list. The user does not exist.

• 421 Resources temporarily unavailable. Please try again later.

The Yahoo! Mail MTAs are temporarily too busy. Your server should try to resend the message after a few minutes.

If you do not see these or similar error messages, you should see an SMTP confirmation code similar to "250 ok dirdel" that indicates your message has been delivered.