Redmine

Currently, the default email address for the built-in admin user is admin@example.net. Although example.net is reserved for documentation, some users still mistake it for a real, reachable email address, since they can access URLs like https://www.example.net/.

I propose changing the default value to: admin@dummy.invalid

This makes it clearer that the address is a dummy and helps avoid confusion.

In addition, according to the section 6.4 of RFC 6761, name resolution for .invalid should immediately fail, so mail servers should not attempt to establish an SMTP connection to that domain.