sendmail邮件发不出去的问题

Question

mailq
/var/spool/mqueue (12 requests)
-----Q-ID----- --Size-- -----Q-Time----- ------------Sender/Recipient-----------
j15ELbB6014443 54 Sat Feb 5 22:21 <attiseve@mail.n24ms.lixia.edu.cn>;
(host map: lookup (163.com): deferred)
<zhaobing8181@163.com>;
j15DkO50009286 56 Sat Feb 5 21:46 <attiseve@mail.n24ms.lixia.edu.cn>;
(host map: lookup (163.com): deferred)
<zhaobing8181@163.com>;
j152iROX007113 57 Sat Feb 5 10:44 <attiseve@mail.n24ms.lixia.edu.cn>;
(host map: lookup (163.com): deferred)
<zhaobing8181@163.com>;
<attiseve@tom.com>;
j139sx8m024310 6 Thu Feb 3 17:55 <attiseve@n24ms.lixia.edu.cn>;
(host map: lookup (163.com): deferred)
<zhaobing8181@163.com>;
j136wg20010514 27904 Thu Feb 3 14:59 <attiseve@n24ms.lixia.edu.cn>;
(host map: lookup (163.com): deferred)
<zhaobing8181@163.com>;

DNS解析没有问题啊，怎么会老是延迟发不出去呢？