'Hi Pillar Box,

Between us, my brothers and I have a number of rentals, and given the success of this rental finding caring tenants, we would be pleased to come back to you in the future.
The choice of the right agency is really important to avoid void periods, and you came back within just days with a suitable tenant.

Thank you for arranging everything smoothly, we will use your company again.

Regards,

Alison Maynard.'