I use exim4 as a send only email on my servers, The FQDM I have on this servers is ws1.example.com (ws1,ws2,ws3...) and the email I use for receiving emails is a different smtp server with the email address being firstname.lastname@example.org , when I send email from my ws[num].example.com servers to any other service like gmail and hotmail everything works fine, also when I send email from any service(gmail,hostname..) to email@example.com everything works fine too, the problem is when I send emails from the ws[num].example.com servers to firstname.lastname@example.org I get "email@example.com: Unrouteable address" . Maybe the servers lookup for the address in the local hosts file since it is the same domain? How do I love it?
Try configuring your server to use the
smarthost option. Use your mail server as the smarthost. If the name resolves to an Internet address, you may need to connect by IP address, add a host entry or configure hairpin NAT to your mail server.