White powder by the vent ?

Can anyone tell me what this accumulation of the white powder is? It seems to be coming from the vent connector of the oil fired furnace. Is it some byproduct of the combustion or is it deteriorated clay liner working its way down the flue connector? Or could it be that the oil being burned is reused/filtered oil, containing some sulfites etc. - there is a reason to believe that the used oil was being burned.

Looks like zinc from the galvanized pipe. If there is condensation inside the vent from combustion gases or from moisture intrusion, it will turn the zinc coating to a white powder. Recommend a Level 2 to make sure there are no blockages or restrictions which would be causing poor venting.

Thanks, I did recommend level 2 inspection.