I can't advise much on the given description.

So, you submitted a proposal for building e-commerce site. This is what I understood.
You need to improve your English a bit. There are a lot of spelling and grammatical mistake.
Try to use a editor like "Grammarly" it's free. It will help.
Also arranging the example site and Core functionality a little more noticeable will do better.
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Hi/ Hello,
.......... YOUR INTRODUCTORY SENTENCES HERE.............. Check our previously built sites/demos.
EXAMPLE SITES:
======================
1. .......
2. .....
3. ......
4. .....
Core functionality we are thinking of:-
1. Admin Functionality:-----------------------------------------------
List them here.
2. Buyer Functionality:-----------------------------------------------
List them here.
3. Front-end Functionality:---------------------------------------------------
List them here.
Please do not list anything unless it is necessary.2-3 more lines to ask for details or point of contact
End with a regards............
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This is not a bad format actually. But the context all depends on the job advertised. As, I said earlier, there are many factors depends on what you should write.