There are 2 ways you can tip your carrier:
1. You can leave an envelope on the door or the porch in a visible location.
2. If you are on autopay, you can add a tip to those payments by visiting the Member Center and updating that payment to include a tip. There is a separate field for this to be added.
https://manage.bostonglobe.com/cs/mc/Login.aspx?p1=BGHeader_ManageAccount