I need to set up a registration form for an event in which the main communication channel between the registered users and the organizers is the e-mail. E-mails could be sent before, during and after the event with informative purposes about such event (i.e. no marketing).
Basically the registration is not possible if the user doesn't want to receive e-mails. For instance, just after the sign up the user would receive a confirmation e-mail.
What should be the canonical way to grant the permission to send e-mails to the user according to GDPR in this case?
If I understood it well, putting a notice like Signing up this event you also consent to receive informative emails from us about the event would not satisfy the regulation about active consent.
Should it be better to give the user the option to agree to receive e-mails, e.g. through option-buttons (e.g. Do you agree to receive e-mails from us to keep you informed about the event — ○ Yes / ○ No) and then refuse to register the user displaying an error message like Sorry, we cannot handle your registration if you don't allow us to send e-mails to you?