Is there any evidence that Gandalf's maia origin was known to Sauron. Not many of the elves even knew (Cirdan, Galadriel and Elrond maybe)
This quote makes me think not.
'So!' said the Messenger. 'Then thou art the spokesman, old greybeard? Have we not heard of thee at whiles, and of thy wanderings, ever hatching plots and mischief at a safe distance? But this time thou hast stuck out thy nose too far, Master Gandalf; and thou shalt see what comes to him who sets his foolish webs before the feet of Sauron the Great. I have tokens that I was bidden to show to thee - to thee in especial, if thou shouldst dare to come.'
The Return of the King: The Black Gate Opens
Is there any evidence to show Sauron knew more? I'd like to think he would have changed his plans if he had known the truth.