Type Aliases The following type aliases are available globally. Progress (Mail, Error) callback after each Mail is sent. Mail is the mail sent and Error is the error if it failed. Declaration Swift public typealias Progress = ((Mail, Error?) -> Void)? Completion ([Mail], [(Mail, Error)]) callback after all Mails have been attempted. [Mail] is an array of successfully sent Mails. [(Mail, Error)] is an array of failed Mails and their corresponding Errors. Declaration Swift public typealias Completion = (([Mail], [(Mail, Error)]) -> Void)?