Problem After Changing Hostname

[ashkev]

In an attempt to have good DNS records, I changed the Hostname on MY ISPConfig server And Postfix from server1.example.com to mail.cass.lib.mi.us. I am running the ISPConfig Virtual Appliance. Now when I try to send mail to e-mails @ cass .lib.mi.us I get this error:

<web2_mjsmith@server1.example.com> (expanded from

<web2_mjsmith@cass.lib.mi.us>): mail for server1.example.com loops back to
myself

What have I missed?

Thanks again for all of your help.

[ashkev]

I changed the hostname in several places as described here.

Now the error I get is this:<web2_mjsmith@server1.example.com> (expanded from <mjsmith@cass.lib.mi.us>):
[server1.example.com]: Name or service not known

[ashkev]

can anyone help me?

[falko]

What's in /etc/postfix/main.cf? What's the output of

hostname

and

hostname -f

?