Need help identifying this part
 

Hello,
I was wondering if someone here can help me identify this part. This belongs on my 2009 Mazda CX 7.
The part has a plastic cap on top, underneath is a flexible rubber type cover. This rubber portion has a rip in it and has spewed some oily type substance on the motor. The only way I knew there was a problem is because there was a strange noise coming from the engine compartment. The plastic cap was off and laying next to and rubbing against the serpentine belt. That's when I noticed the oily mixture on part of the engine and saw the tear in the rubber. I'm trying to figure out what this part is and what it does. There a small blue arrow pointing to the part.
Thanks for your help.

That is your main engine mount.

Great, thank you so much.