Mail Issue - Server name issues

I am having issues changing my hostname/domain so it is a DNS name that other mail servers can resolve as messages are being bounced.

Background - E-mail does work if I send to the domains hosted. As well, e-mail can be replied to in round cube webmail just fine. I am using a PHP script on a domain and this is where the problem is occurring. I am trying to send a confirmation to the user that has filled out the form. This is ISPConifg on a Fedora Core 6 Box.

I know that this is a hostname issue and that is should be an actual domain name appended onto the hostname but right now it is firestorm.localdomain

hostname -f
firestorm.localdomain

cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost.localdomain localhost
10.1.250.5 firestorm.localdomain firestorm

[root@firestorm postfix]# cat local-host-names
###################################
#
# ISPConfig local-host-names Configuration File
# Version 1.0
#
###################################
localhost
firestorm.localdomain
localhost.firestorm.compassit.ca
localhost.compassit.ca
localhost.localdomain
www.compassit.ca
compassit.ca
#### MAKE MANUAL ENTRIES BELOW THIS LINE! ####

If I change the hostname to firestorm.compassit.ca (which is my actual local domain) in etc/hosts and in /etc/postfix/local-host-names then my e-mail doesn't work at all. It says that the type A record could not be found.

Ok, so here is the mail error before I make the changes to the hostname
Jan 13 08:13:26 firestorm postfix/smtp[20274]: D784DB016F: to=<[email protected]>, relay=mx.svc.telus.net[199.185.220.200]:25, delay=0.45, delays=0.11/0.02/0.22/0.1, dsn=4.0.0, status=deferred (host mx.svc.telus.net[199.185.220.200] said: 450 <[email protected]>: Sender address rejected: Domain not found (in reply to RCPT TO command))


And here is the error once I change the hostname around to firestorm.compassit.ca and restart postfix:
Jan 13 08:31:38 firestorm postfix/smtp[20693]: 7EE4AB0170: to=<[email protected]>, orig_to=<[email protected]>, relay=none, delay=0.05, delays=0.01/0/0.04/0, dsn=5.4.4, status=bounced (Host or domain name not found. Name service error for name=firestorm.localdomain type=A: Host not found)

It seems that something is still looking for firestorm.localdomain but I am not sure where or what other files to configure. (The mail can now be delivered to the ISP's mail system but internal e-mail going to the domain no longer works - same error as above)

Am I missing some other settings for this or is my thinking off?

Thanks in advance

 

Thanks for the info Till, however, after making the changes you suggested I know get a different error. This is when sending an e-mail outside of the server into a hosted domain.

Jan 13 13:57:43 firestorm postfix/smtp[25808]: E1B25B0174: to=<[email protected]>, orig_to=<[email protected]>, relay=none, delay=0.24, delays=0.16/0/0.08/0, dsn=5.4.6, status=bounced (mail for firestorm.compassit.ca loops back to myself)

As well Till, I did not have a localhost.localdomain in the postfix main.cf file (output below - nothing shows up for localhost.localdomain)

[root@firestorm postfix]# cat main.cf | grep localhost
#inet_interfaces = $myhostname, localhost
# The default is $myhostname + localhost.$mydomain. On a mail domain
#mydestination = $myhostname, localhost.$mydomain, localhost
##mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
##mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain,


Any thoughts now?

Thanks,