Our host had Cpanel 4.7 and after upgrading to 4.8 all our Mailing lists are giving problem, non of the existing lists sends mails and when we try to create a new list getting the following error:

Entry for aliases file:

## testmail_akaize.com mailing list
## created: 31-May-2002 akaize
testmail_akaize.com: "|/usr/local/cpanel/3rdparty/mailman/mail/wrapper post testmail_akaize.com"
testmail_akaize.com-admin: "|/usr/local/cpanel/3rdparty/mailman/mail/wrapper mailowner testmail_akaize.com"
testmail_akaize.com-request: "|/usr/local/cpanel/3rdparty/mailman/mail/wrapper mailcmd testmail_akaize.com"
testmail_akaize.com-owner: testmail_akaize.com-admin

Hit enter to continue with testmail_akaize.com owner notification...
Traceback (innermost last):
File "/usr/local/cpanel/3rdparty/mailman/bin/newlist", line 220, in ?
main()
File "/usr/local/cpanel/3rdparty/mailman/bin/newlist", line 213, in main
text)
File "/usr/local/cpanel/3rdparty/mailman/Mailman/Message.py", line 211, in __init__
OutgoingMessage.__init__(self, text)
File "/usr/local/cpanel/3rdparty/mailman/Mailman/Message.py", line 205, in __init__
self['Message-ID'] = Utils.make_msgid(idstring='Mailman')
File "/usr/local/cpanel/3rdparty/mailman/Mailman/Utils.py", line 764, in make_msgid
idhost = socket.gethostbyaddr(socket.gethostname())[0]
socket.error: host not found


Need some support please?

Try adding entries in /etc/resolv.conf

search <your domain name>
domain <your domain name>
nameserver <your nameserver addr>