We'd love to have the ability to send out personalized emails to groups of donors on BetterWorld -- and we're working on it!
For now, the best way to email guests is to download a list of their emails, and then import them into whatever mail client you're using (Active Campaign, Gmail, MailChimp, etc.).
To export a list of guests' emails from your dashboard click Ticketed Events on the left side menu and then click Manage on your event. Then click Attendees on the left side menu.
On the Attendees page click the Export Attendees button at the top of the page.
Then choose from the dropdown menu the ticket type you would like to export or the all guests option. Click export and a CSV file with all of the attendee's information (including email) will automatically download to your device.