Research and figure out what would the be best way to send emails in batch through the Postmark API.
See "Send batch emails" at Sending emails docs at Postmark.
Supporting this in a SwiftMailer transport may not even be a best-practice though.
See also Sending emails in batch with SwiftMailer and this StackOverflow comment stating SwiftMailer removed such functionality.
Research and figure out what would the be best way to send emails in batch through the Postmark API.
See "Send batch emails" at Sending emails docs at Postmark.
Supporting this in a SwiftMailer transport may not even be a best-practice though.
See also Sending emails in batch with SwiftMailer and this StackOverflow comment stating SwiftMailer removed such functionality.