It seems that our validator doesn’t consider arbitrary amount of domains and sub-domains. I’ve created an issue on GitHub: link.
You can create your own implementation of EmailValidator and use it instead of default. Probably you will need to override default screen to replace a validator, for example on User editor screen.
Thanks for the confirmation. So, chances are that we will have a fix some day.
Regarding “override default screen”, is there a link explaining how to do that step by step (or a sample project)?
I can see a lot of answers that mention override. I guess this is something very simple. However, it is so simple that no one wasted time documenting this .