C#: Window Service with thread pool

Hello Folks,

FYI, actually, I need to send emails from multiple databases (schema is same) then, I would like to use thread pool.
I would like to create a window service in C# which will be having below features:

1. I would like to use Thread Pool in window service;
2. The threads will be configurable like 2 threads.
3. The chunk size will be configurable like 5 i.e. records chunk size.
4. Could you please provide me code snippet for this?
Like,
a.) Aforesaid 1 to 3 points
b.) I need to put logic to utilize threads once idle. For example, two threads (using Thread Pool) are running in window service;
c.) And 500 emails need to send;
d.) Pre-assume, we have set 2 threads and 5 records chunk size; That means, 10 records records are processing in two threads
e.) So, window service logic should not wait to complete 10 records. In case one of the thread is free then assign next 5 records chunk size.

Best Regards,
Mohit Pandit