What do the icons/emojis mean on the appointments?

The icon/emoji on an appointment represents various status updates related to the text reminder:

• An open envelope means that a text reminder is queued and ready to be sent but has not been sent yet.
• A closed envelope means that a text reminder has been sent to the customer.
• A clipboard with an "X" means that the customer has responded to the appointment reminder and has indicated they are interested in cancelling the appointment.
• A clipboard with a magnifying glass means that the customer has responded with a desire to reschedule or has sent a comment.  You can view this comment by tapping on the appointment and tapping NOTES or tapping on the customer and then tapping NOTES.
• A clipboard with a check mark means the customer has responded and confirmed the appointment.