OK, I know this problem has been covered so many times, so please excuse if the answer is right under my nose (i did quite a bit of searching, though...)
I have a website, http://www.ritochpowell.com
where mail is hosted in their office, on their exchange server (DNS is not managed by ISPConfig, rather at net-sol)
The website is set to External Mailserver
There are no MX records
IS in etc/postfix//local-host-names (if I delete this, I get about 1 email before it is added back to the file
I can not send mail to firstname.lastname@example.org
Where am I going wrong?