aaPanel_Kern what @Edu3D say is true.
The forward function does not work correctly.
The definition of forward rules must be inverted. Actually when you define a forward it does not forward the email from the destination user to the email account but on the contrary.
When you define the mail forward
You see the "Forwarded users" that is the real mailbox address and on bottom "Receiving user" should be the "alias" but the generated rule is reverse.