exim (unrouteable mail domain)

[xploit]

my server has been working fine,i just updated lately to :
WHM 9.4.0 cPanel 9.4.1-S65
RedHat Enterprise 3 - WHM X v3.1.0

two days later,a user with xxx.yyy.com at my server reported that whenever he sends an email to yy@china-inse.com he get this error:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

yy@china-inse.com
unrouteable mail domain "china-inse.com"

when i dig for the MX records for this domain from my server,it resolves.

when i check from the ssh using : /usr/sbin/exim -bt -d inse@china-inse.com
i get the following :

Exim version 4.34 uid=0 gid=0 pid=23956 D=fbb95cfd
Berkeley DB: Sleepycat Software: Berkeley DB 4.1.25: (August 21, 2003)
Support for: iconv() PAM Perl OpenSSL
Lookups: lsearch wildlsearch nwildlsearch iplsearch dbm dbmnz
Authenticators: cram_md5 plaintext spa
Routers: accept dnslookup ipliteral manualroute queryprogram redirect
Transports: appendfile autoreply pipe smtp
changed uid/gid: forcing real = effective
  uid=0 gid=0 pid=23956
  auxiliary group list: <none>
configuration file is /etc/exim.conf
log selectors = 00000ffc 00010400
trusted user
admin user
originator: uid=0 gid=0 login=root name=root
sender address = root@mercury.xool.net
Address testing: uid=0 gid=12 euid=0 egid=12
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Testing inse@china-inse.com
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Considering inse@china-inse.com
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
routing yy@china-inse.com
--------> defer_router router <--------
local_part=yy domain=china-inse.com
calling defer_router router
rda_interpret (string): :defer: All deliveries are handled by MailScanner
expanded: :defer: All deliveries are handled by MailScanner
file is not a filter file
parse_forward_list: :defer: All deliveries are handled by MailScanner
extract item: :defer: All deliveries are handled by MailScanner
defer_router router: defer for yy@china-inse.com
  message: All deliveries are handled by MailScanner
yy@china-inse.com cannot be resolved at this time:
  All deliveries are handled by MailScanner
search_tidyup called
>>>>>>>>>>>>>>>> Exim pid=23956 terminating with rc=1 >>>>>>>>>>>>>>>>

everything is working fine with me.except this domain.
exim log files gives me no clues at all.

any ideas ?

[chirpy]

All the exim output you quoted shows is that mail delivery is handled by MailScanner, so is not at all helpful. However, this:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

yy@china-inse.com
unrouteable mail domain "china-inse.com"

is not coming from your server, but from the one at the end of china-inse.com, and indicates a problem on that server, not yours. The message would indicate that the remote server has not been setup to relay email for that domain.

[xploit]

ok,the strange thing is that i can send from the web without problems,and no mails are returned.
however,when i send using the outlook it returns with the email msg above.

and please notice,sending by outlook is the one with the problem,not with webmail!

so any ideas please !