I have seen a similar topic here, but unable to figure out the solution derived from that topic. Since I am new here I hope someone would help me simplify the solution for this issue. Here is it: I had created my box with email@example.com. Now I need to create a user on a different domain name which is firstname.lastname@example.org. But the system says this: “You may not make a user account for that address because it is frequently used for domain control validation. Use an alias instead if necessary”.