各位前輩好
小弟所在公司是在台灣，最近有大陸分公司員工反映，無法寄信給大陸特定公司會被退信，
有時從特定公司那邊寄過來的信也會收不到，
因為AD網域以及mail server是從總公司這邊來架設，所以請我查看一下
這是我SMTP log(in)
<-- MAIL FROM:<bbb.com.tw> SIZE=6763
--> 250 <bbb.com.tw>, Sender ok
Performing DNS-BL lookup (100.65.20.215 - connecting IP)
cl.spamcop.net - passed
zen.spamhass.org - passed
---- End DNS-BL results
250 <aaa.com>, Recipient ok
250 Ok, message saved <Message-ID: E19DC0A8160B91478F5D6D2D7876C8293C9335@bbb.com.tw>
Connection closed
SMTP session successful (Bytes in/out: 6887/439)
Tue 2015-09-08 09:25:57: Accepting SMTP connection from [191.195.100.122:53486] to [192.168.1.2:25]
Tue 2015-09-08 09:25:57: Performing PTR lookup (122.100.195.199.IN-ADDR.ARPA)
Tue 2015-09-08 09:26:27: * DNS: 30 second wait for DNS response exceeded (DNS Server: 168.95.1.1)
Tue 2015-09-08 09:27:27: * DNS: 30 second wait for DNS response exceeded (DNS Server: 8.8.8.8)
Tue 2015-09-08 09:27:27: * Error: * Name server reports domain name unknown
Tue 2015-09-08 09:27:27: * MDaemon configured to drop connection when domain name unknown
Tue 2015-09-08 09:27:27: ---- End PTR results

這是我SMTP log(out)
Attempting SMTP connection to [bbb.com.tw]
Resolving MX records for [bbb.com.tw] (DNS Server: 192.168.1.1)...
Name server has no valid records of the requested type for that domain
Resolving MX records for [bbb.com.tw] (DNS Server: 192.168.2.2)...
Name server has no valid records of the requested type for that domain
Tue 2015-09-08 01:24:31: Resolving MX records for [bbb.com.tw (DNS Server: 168.95.1.1)...
Tue 2015-09-08 01:27:03: Attempting SMTP connection to [bbb.com.tw:25]
Tue 2015-09-08 01:27:03: Resolving A record for [bbb.com.tw] (DNS Server: 8.8.8.8)...
Tue 2015-09-08 01:27:33: * DNS: 30 second wait for DNS response exceeded (DNS Server: 8.8.8.8)
Tue 2015-09-08 01:27:33: This message is 0 days old; it has 2 days left to get delivered
Tue 2015-09-08 01:27:33: SMTP session terminated (Bytes in/out: 0/0)
小弟看起來是DNS的問題，只是問題是在我方嗎
謝謝