I noticed that the EM-client is creating a Message-ID “random@[computer name]”.
and mail servers are worse for such letters and sometimes put in spam.
Suggestion:
make an additional checkbox in the settings, which changes the setting Message-ID - Message-ID random@[sender domain].
Message-ID random@[sender domain] configured by default in the following email clients:
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. 