Hi @Artur,

Thanks for reaching out to the Community Forum! 

Double opt-in is set at the list level and by default it is enabled for each of your lists. In order to disable double opt-in, you’ll need to click into the list’s settings and switch that list to single opt-in. By switching to single opt-in, a user that signs up for email marketing will automatically get added to the list rather than needing to confirm their email address through the double opt-in email. This help center article will show you how to do this as well as highlight the pros and cons of single opt-in.

Have a great rest of your weekend!

Julie