Using Marketing - Mailings - Create Mailing you can send marketing emails with information about upcoming events, emails with free tickets or just a simple email, but in your own house style.
First, determine the layout. You make this using Settings - Marketing - Email themes. Choose 'Create theme' at the top right to create a new theme. Name the theme, set the colours, choose a font and add your own logo. Return to Marketing - Mailings - Create Mailing to further format the mail.
You can link the theme to a ticket shop using Settings - Ticketing - Ticket Shops. As a result, the ticket emails that visitors receive are also styled to this specific theme.