Not able to send mail from local mx to external mx
I manage several domains on my debian server with ISPConfig some of them have local mailservers but some not, now I'm not able to send emails from domains with a local mailserver to those domains which has an external mailserver. I have also set the external mailserver option under "options" but anyway I get the following error: "550 <firstname.lastname@example.org>: Recipient address rejected: User unknown in local recipient table", it means that the malserver is looking for the mailbox on the local server which is not present since they are external. When I have configured the Domains without a local mailserver I also have checked out the option to create the mx records. Can you please explain me how to fix this issue, thanx in advance!