replies sent from the envelope icon in upper right corner are so not appear in Email section of contact or deal record

replies sent from the envelope icon in upper right corner are so not appear in Email section of contact or deal record

Hello, 
I am corresponding with a contact about a deal. If I reply to the contact's email by clicking the envelope icon in the upper right corner, then hitting reply icon and sending a reply, that reply is not shown in the email section of either the contact or deal module. The contact confirms that the received the email. I would expect a record of my reply to, at least, appear in the Deal module's Email section because the reply was related to the Deal. What's going on?