For a TMail, you can add a Receipt Acknowledgement and send it to all associated Writers to indicate that you have received a particular Message.
In Navigation, select the Message or TMail Pin corresponding to the TMail for which you want to add a Receipt Acknowledgement. For example, you can select a Message in Inbox folder, or a TMail Pin inTMail Pins | Recent. (Please see Navigation for more details.)
In the right hand side, locate the specific Comment for which you want to add a Receipt Acknowledgment. Click on the small down arrow for this Comment, as below.
Select Add Receipt Ack option. TMail21 shows you the details of Receipt Acknowledgement that you have received comments from #1 to #n where n is the selected Changeset, as below.
Click on Acknowledge Receipt. A changeset is added to the TMail indicating that you have received the Comments. An Acknowledgement Receipt icon also appears as shown below.