To have a functioning account system, we store our users' email addresses. Similarly, if you login through any third party services, we store the associated account IDs of those services, along with access tokens that can be revoked by you at any time.
For those of you who use third party login options (Patreon, Google, Discord, and Facebook), we store the email address provided by the third party service, as well as the user ID for that account, in order to associate you with your Drawabox.com account. That information is not used for any other purposes other than authentication, and is never made available to any other parties.
Currently there is no automated system for deleting your data, but you can send an email to email@example.com from the address associated with the account whose data you'd like to delete and it will be addressed within a few days.