Wot?

If you have a skydome / envirosphere / background plane etc. with an HDR image on it (or any kind of image for that matter), it will be reflected by a Poser reflection node.

Where did you get the idea that Poser doesn't do this?

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)