为什么不能发到sina.com的信箱？

tenlau

但是可以发到其它信箱，退信：<br>
This is an automatically generated Delivery Status Notification.<br>
<br>
THIS IS A WARNING MESSAGE ONLY.<br>
<br>
YOU DO NOT NEED TO RESEND YOUR MESSAGE.<br>
<br>
Delivery to the following recipients has been delayed.<br>
<br>
是什么原因？