Hello, on a server running ISPconfig3 I set up a website (mydomain.com) that uses an external mailserver. On my website I have several webforms that are supposed to deliver their contents to an firstname.lastname@example.org but these mails are not delieverd. When I change the form receiver to an address on a different domain, that is not hosted on this machine, it works fine. So I tried to send an email from a different domain that is hosted on the same server, but I get an error: Requested action not taken: mailbox unavailable 550 5.1.1 <email@example.com>: Recipient address rejected: User unknown in local recipient table For my domain (the one with the external mailserver) I had not set up a mail domain in ISPconfig3, so I tried to create one and disable it, but this didn't help either. Receiving mails from domains that are not hosted on this machine works fine. How can I accomplish that emails that are sent from this server are not locally delivered but are sent to the right mailserver (according to the correctly set MX record).