email

type Delivery int

type Message struct {
	To      string
	Subject string
	Text    string
}

type Sender interface {
	// Send hands m to the provider and returns the provider's ID for it. A nil error
	// means the provider accepted the message, not that it arrived.
	Send(ctx context.Context, m Message) (id string, err error)
}

type Tracker interface {
	// Delivery returns the state of the message with the given ID and, once it was
	// delivered, when.
	Delivery(ctx context.Context, id string) (Delivery, time.Time, error)
}

type TrackingSender interface {
	Sender
	Tracker
}