OrderlyEmails does not send any emails itself, so it cannot help with marketing or mass emails to your customers and subscribers.
The app is a design tool which upgrades the emails that Shopify is sending for your store. So your store continues to work in exactly the same way as before, but now with much better emails.
Because Shopify does not have a feature to send marketing or mass emails, OrderlyEmails cannot either.
To send marketing or mass emails, we recommend using an email marketing platform like MailChimp or Klaviyo.