@SolusVM See @Gary reply below on the local computer name in the message header.
Setting Message-id - Mail - eM Client
The standard is .
If you are sending mail through your company’s own mail server, it should be the actual domain and not the host name of your computer. That is what happens for me, but when I send personal mail from home through my ISP, the host name of the computer is used. I always understood that this is the required method.
If you want to change the way this is generated without changing the application, just change the host name of your computer. Otherwise, if you want to change OS and mail clients, some Linux clients do allow you to configure your message-id as you have suggested. 