Email sent to Yahoo Mail addresses is rejected

Yahoo Mail rarely outright rejects email upon connection. If you're an email administrator, Yahoo recommends that you review the associated SMTP logs for any of the errors below:

• "553 VS99-IP1 deferred" - This error means your SMTP connection was rejected.
• "451 VS1-IP Excessive unknown recipients - possible Open Relay (#4.1.8)" - means the email was deprioritized (see our guidelines on avoiding deprioritization)
• "451 VS1-MF Excessive unknown recipients - possible Open Relay (#4.4.5)" - means the email was deprioritized (see our guidelines on avoiding deprioritization)
• "554 delivery error: dd This user doesn't have a yahoo.com account ([recipients' userid]@yahoo.com)" - The email didn't go through because the recipient's user ID doesn't exist. You shouldn't retry the message, as it will never complete successfully.
• "421 Resources temporarily unavailable. Please try again later" - The Yahoo Mail servers are temporarily too busy. Your server should try to resend the message after a few minutes.

If you don't see these, or similar error messages, the emails in question aren't being blocked or deprioritized. You should see an SMTP confirmation code similar to "250 ok dirdel" that indicates your message has been delivered.

从官方的解释可以看出，250 ok dirdel表明，邮件是投递成功的。这里的dirdel中的del代表的不是删除的意思，如果邮件没在收件箱，那么可能是某个原因导致邮件进了垃圾箱等，可以尝试关闭雅虎的反垃圾设置或直接去垃圾邮件里面查找该邮件。