Okay, so, you press sign up on the combat arms homepage and enter your email in. Double check both of them are exactly the same. If the error continues to occur, either create a new email or send nexon a ticket via customer support.
That's why you make sure Both emails are 100% the same .
Example : Thisisafakeemail123@Yahoo.com
If you capitalize a letter you would have to do the Exact same thing to the other .
If you keep experiencing this problem send a Ticket to Via Nexon .