Postfix is running and I can send and receive emails but when I do some change on others seccion of webmin I can’t save new configuration because I get this message:

Falla al guardar opciones habilitadas : Your Postfix configuration is missing the system’s mail hostname localdomain from the mydestination line, which will cause mail to bounce.

Can someone help me please?

Ok, I dont’t understand how Postfix worked, but only it needed to bie configured…