Service unavailable 是何问题

红泥花生

Service unavailable 但是能收到对方发来的邮件,也能正常收发其他人的邮件.这是什么问题

==================
Solaris 8 + Sendmail的环境

========在LOG里有错误信息=========
/var/log/syslog:Nov  3 14:54:02 localhost sendmail[3938]: [ID 801593 mail.info] iA36ru403936: to=grandis@kit.hi-ho.ne.jp,
ctladdr=root (0/1), delay=00:00:06, xdelay=00:00:05, mailer=esmtp, pri=120083, relay=kit.hi-ho.ne.jp. [202.224.159.144],
dsn=5.0.0, stat=Service unavailable

/var/log/syslog:Nov  3 14:54:02 localhost sendmail[3938]: [ID 801593 mail.info] iA36ru403936: iA36s2303938: DSN: Service u
navailable

==================本地的DNS解析没有问题=======
local:root 104 >; nslookup -q=MX
Default Server:  ns1.imsbiz.com
Address:  206.161.62.6

>; kit.hi-ho.ne.jp
Server:  ns1.imsbiz.com
Address:  206.161.62.6

Non-authoritative answer:
kit.hi-ho.ne.jp preference = 10, mail exchanger = kit.hi-ho.ne.jp

Authoritative answers can be found from:
hi-ho.ne.jp     nameserver = dns1.pana.net
hi-ho.ne.jp     nameserver = dns0.pana.net
kit.hi-ho.ne.jp internet address = 202.224.159.144
dns0.pana.net   internet address = 218.42.190.103
dns1.pana.net   internet address = 202.224.158.167

================ 也可以正常ping对方===========
PING 202.224.159.144: 56 data bytes
64 bytes from kit.hi-ho.ne.jp (202.224.159.144): icmp_seq=0. time=288. ms
64 bytes from kit.hi-ho.ne.jp (202.224.159.144): icmp_seq=1. time=668. ms
64 bytes from kit.hi-ho.ne.jp (202.224.159.144): icmp_seq=2. time=295. ms

========用window NT + EXCHANGE5.5的环境发,弹回错误信息=====
========也不能发送邮件到对方,会弹回一个错误信息=====
The following recipient(s) could not be reached:
>;
>;       'grandis@kit.hi-ho.ne.jp' on 11/3/2004 10:52 AM
>;             The recipient was unavailable to take delivery of the message
>;             MSEXCH:IMS:Integrated Concepts International
>; Limited:ICILHK:ICILEXCH 3554 (000B09AA) 554 Invalid sender IP address