Navigate to the 'Letters' section in your application.
Click on 'Templates' in the left sidebar, choose a template you want to modify and select 'Edit template'.
In the left sidebar, find the field labeled {{firstName}}. Type the default recipient name you wish to use, e.g., "Homeowner" and click the 'Save template' button located at the top right corner.
When you add this template to your mailshot, all letters within that mailshot will be addressed using the default name you've chosen.