Unknown substance in sink drain

[Ulysses]

My sink emits a whiff of something when hot water is used. It isn't the water itself. I've used bleach-based drain cleaners and soda and vinegar to no effect. I took a good look down the drain and found the attached. Whoa.

It isn't scoopable. It feels more like soft rubber and is a single piece. Is it a wrecked discolored mildewy seal or robust biofilth?

 

[snowhead]

My guess would be silicone sealant that someone has been over enthusiastic with.
It won't be the cause of the smell, but may cause sustances to ckling to it.

 

[moonlight]

That's silicone sealant. Have you taken the trap off? how long has it been smelling. Do you have a dishwasher feeding in below? Has anything new been added to your waste system?