Relay mail server

Hi,

I have a postfix mail server on centos 6. (mailserver.mydomain.com )

I want to send mail through my mail server from other linux server ( server1 ), so that it will use mail server IP address.

I have tried.

myhostname = server1.mydomain.com 
relayhost = mailserver.mydomain.com 

in client server ( say server1 ) postfix configuration. and restarted postfix.

but when i am sending mail form server1.

It is going but when i am checking full path of mail, it is showing

Received: from server1.mydomain.com 

rather then

Received: from mailserver.mydomain.com

Can some one please let me know what is wrong in my configuration.

MY CONF on Client side.

queue_directory = /var/spool/postfix
command_directory = /usr/sbin
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
mail_owner = postfix
inet_interfaces = localhost
inet_protocols = all
mydestination = $myhostname, localhost.$mydomain, localhost
unknown_local_recipient_reject_code = 550
myhostname = server1.mydomain.com 
relayhost = mailserver.mydomain.com
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases


debug_peer_level = 2
debugger_command =
         PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin
         ddd $daemon_directory/$process_name $process_id & sleep 5
sendmail_path = /usr/sbin/sendmail.postfix
newaliases_path = /usr/bin/newaliases.postfix
mailq_path = /usr/bin/mailq.postfix
setgid_group = postdrop
html_directory = no
manpage_directory = /usr/share/man
sample_directory = /usr/share/doc/postfix-2.6.6/samples
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES

Add

mydomain=mydomain.com

I have added the same and restarted postfix in client server.
but no luck.

mydomain = mydomain.com