Hi @ivalanciute633,
Marketing tools like email campaigns are available through your SimplyBook.me account; you can enable these tools in the SimplyBook.me admin interface. Please find a list of available options/integrations here: https://simplybook.me/en/marketing-tools
These are not integrations inside the WordPress plugin itself, though. The WordPress plugin connects your site to SimplyBook.me so you can show the booking calendar/widget and manage bookings from WordPress. Features such as email campaigns, coupons and marketing tools live in the SimplyBook.me platform (marketing tools overview).
Let me know if you have any questions about this.
Kind regards, Jarno