How to add to the project team, api consoles not a member of the App Engine domain?

Question

Google

Today I tried to give access to the client so that he himself monitors the limits in the console, but he could not add it.
The eloquent entry flaunts
Only users in domain simple.com may be added to the project.
At the same time, if you select a simple user [email protected], then he does not have such a restriction.