Here si the second e-mail form WG which probably explain it.
COMMANDER
Recently you may have received an email from us regarding test ships being credited to your account.
This email was meant to be sent to our community of Supertesters only, but was delivered to you by mistake.
We sincerely apologize for causing any confusion and we will make sure this does not happen again.
However, if this incident sparked your interest in helping us test and improve World of Warships, feel free to keep an eye on dedicated forums, as recruitment topics pop up from time to time.
Action Stations!