[CentOS] postfix - hostname

Hi,

I have this problem

my email server's DNS name is

ns1.mydomain.com, and it is registered in the reverse DNS also with that name, when i installed my server at the hostname i entered

centos-server.mydomain.com

when i tried to send an email from the root console with

# mail root

the email is returned saying that

root@centos-server.mydomain.com, could not be verified

i used the command # hostname ns1.mydomain.com and also edited the file.

/etc/hosts, but i have the same result, the hostname did not change, i even restart my server with no luck.

what am I missing?

regards,

Guillermo. PS my server is a CentOS 4.4, with postfix