POSTFIX server, new domain emails stuck in queue
I am newbie to postfix. I added a new domain to my postfix server in the main.cf under mydestinations variable and the relay_domains file. Also, added this domain to my backend exchange server. When I send a test message from the new domain, my messages from that domain appear to be stuck in the "queue active". What does it mean when you are stuck in this queue? Does this mean that my backend email server (exchange 2003) isn't allowing messages from this new domain OR that the POSTFIX server still needs configuring.
Thanks for any help.