Confirming Locations in Remote Areas

Hi, and thanks in advance. 

I have a vacation rental property on a small island in Vanuatu. Part of the Booking sign-up sequence is to confirm the location by allowing Booking.com to send a letter to the address, and then entering the code found in the letter when it arrives. 

Trouble is there is no address (past that of the island name) and no postal service even if there was one. I had similar difficulties having the location identified on Google maps, but got there in the end,. but it took several attempts. 

If anyone has had similar challenge-, or know of an alternative that Booking.com will listen to, I would appreciate a work around.