There is no email confirmation that is sent out once registered. To check if you are registered for the 2018 International Battle Pass Rewards program you can go to the following link to enter or edit your shipping information: https://dota2.cmdvault.com/auth/openid/login/
You will be able to see which Rewards you are registered for as well as the status of each Reward as shown below.
If you’re unable to login, we did not find a registered shipping address associated with this Steam account. Make sure that you are logging in with a Steam ID that has an eligible 2018 Battle Pass level (2017 for Roshan recipients) and submitted a shipping address during the registration window. If you feel as though this is still in error, please contact us through the Support Widget by choosing the "I am registered but cannot login" option.