Hi @HarryM,
Sorry for late reply. So let me just confirm my understanding....
When you select a [to recipient] that has an external email address that is not in your domain, so for example me@gmail.com, you are saying the report sends ok but the from address is @live.hornbill.com even though the from address in the report is set to support@yourdomain.
I will try replicate and get back to you.
Cheers