Mouth of Sauron at Erebor ?

[Boromir88]

If Sauron took the decision to send forth the Nazgul in late June, how could it be possible that one of them had visited the Dwarves in Erebor some months before?~TM

I think Legate made a good explanation at that possibility...now that's only a theory, but at least we know it's possible.

At the time, as we are told in the UT, Khamul was in charge of finding out information about the whereabouts of Gollum.

I'll take a look back into the UT to see exactly when we are talking about here and the situation. But, I've always had the feeling that Sauron didn't want to recapture Gollum. He had found out as much information from Gollum as he could get, and then simply let Gollum go to see if Gollum would lead him to the Ring. So, he wanted to find Gollum's whereabouts to track him and see if Gollum would lead them to the Ring.

I think since we aren't told exactly who the messenger is, of course nobody here can say definitively. I was told a while ago that:
'If it look like a Nazgul,
sounds like a Nazgul,
acts like a Nazgul,
chances are it's a Nazgul'
So, that's kind of been my thinking. However, I admit it's kind of like the race of Gothmog...we aren't told for sure, so we don't know. We can make some educated answers, but can never really be certain. Don't you just love how it's like that; there will never be a time when we can find 'all the answers.'