I am working in Germany since February, 2016 and I have a blue card which is valid till 2020. Due to some reasons am resigning my current job and leaving Germany permanently and moving back to my home country (non EU country). I know I have to inform foreign office if I switch jobs within first two years of getting a blue card. But there are no clear rules about what to do with the blue card while leaving Germany? I checked the foreign office website and there are no details regarding this.
Normally a Blue Card is obtained after you pass some strict requirements. This gives you a residence and work permit in Germany for the first 2 years of your stay, plus access to other benefits. No integration course needed, proof of German language, etc....
If you are not currently working, it's required that you notify the Ausländerbehörde about this. The reason the Blue Card exists is to attract skilled workers when the internal market lacks such individuals. I would also inform them of the reason why are you leaving, including your nationality, as this can help them prevent such things from happening in the future.
They have a public phone number you can call, or email them, or you can write them via post. Their public contact page.