SoapUi - Soap WS addressing, default value for To

What value is used for the WSA:To field when selecting the checkbox "Add default wsa:to" ?

I've been interacting with an external webservice over soapUI that responds correctly when i click this check box, however i can't seem to identify a value to place in the wsa:to soap header that causes this remote webservice to respond the same as clicking this checkbox.

 

The reason i'm doing this is that i need to reproduce this functionality in a separate tool that doesn't allow me to simply select a checkbox to select a default value and i'll need to provide it with either a hard-coded value or some logic to generate the value. 

 

Thanks!