Markus is right. The NethServer domain part of its FQDN determines the “mail” domain. It’s a requirement that you set it to a public DNS domain, if you want to set up a mail server.
I want to point out also that with local AD provider, the
userPrincipalName attribute is synchronized automatically with the mail domain. So you can log on from windows workstations also with the mail address. In your example both
firstname.lastname@example.org are good as Windows logins, as long as the NetBIOS domain form,
In NethServer the following user names are considered valid:
Furthermore, SSSD recognizes also:
…but applications might not allow them.
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There are two main use cases about DNS:
- NethServer AD member (even when it hosts a local AD provider) and mail server
- NethServer just AD member (i.e. File Server)
The first one requires NethServer has public DNS domain to make SMTP work. As said AD has a private, internal DNS zone - a third level domain is recommended, but weird .local .lan & co can work for pre-existing networks.
In the second case, NethServer should be in the same DNS domain of the AD domain (private).