at this moment as far as i know it is not possible from game. However there is 2 ways to find out what is your email adress connected to your account.
One way is to contact support send them some payment IDs to proove account is yours and i think there should not be any problems in getting your email connected to your game account. (ofcourse this is only a suggestion i am not sure they will give you email)
Second way is to use Forgotten password option from login page, type your username and pw will be sent to your mail, however this is only working if you know all emails you use atm and check them all, if you are true owner of the account pw will be sent to your email or the one of the emails you are using.