I have this problem with some MAIL-Server that see my email as Spam.I need to change the HOSTNAME inside the outbound email. The value inside the outbound email is the “Fully qualified Internet host name” that in my case is "ACMESRV1.acme.local; I need to put something like “MAIL.ACME.COM”.
Inside E-mail I see:
Received: from ACMESRV1.acme.local
instead of (what I want to do):
Received: from MAIL.ACME.COM