Our domain is x.corp. Exchange server in domain is mail.x.corp. Some email servers are not accepting our emails because they expect to see recieved from mail.x.com instead of mail.x.corp when they get email from firstname.lastname@example.org.
How many ways are there to fix this and which is the easiest? For example instead of trying to change the domain name which I consider not easy, I thought maybe I can add a record in DNS where mail.x.corp and mail.x.com are the same.