How did Sauron not notice Gandalf sneaking about in Dol Guldur?

Maia are said to sense each other’s presence. I know Gandalf was in disguise but it just seems that he got into Dol Guldur then the dungeons then escaped a bit too easy. It might be possible that Sauron knew Gandalf had entered Dol Guldur but wasn't powerful enough to confront him yet.

So how did Gandalf accomplish such a feat without getting noticed?