ᐅ Sealing the Heating Pipe Where It Penetrates the Wall

Hi!
What is the best way to seal the connection between the stove pipe (oil heating) and the wall connection/chimney?
I read that there is a special type of silicone, but it can attack certain metals like zinc and copper.
How can I tell what metal the pipe is made of, or are there better options to make the seal airtight?
When the heating turns on, you can smell it.
I took some photos.
Maybe someone can give me a tip.

You should have a professional handle that, because there should be no smell at all – if only because of the chimney effect!

In my case, nothing is sealed there, as it is not necessary – the stainless steel pipe fits right inside the fireclay flue liner...

Although it’s a solid-fuel chimney, that doesn’t really matter in this case.

Could the draft be blocked?

I would also first open the vent at the bottom and use a mirror to look inside to see if a bird has built a nest there. The chimney should be drawing properly.