Hello, and welcome to Using English.
1. We don't use "Good afternoon!" in a business letter.
2. Not every business person is male. Do you know the name of your contact at the supplier? In my company, we know who we work with. If you don't, use "Dear Sir or Madam."
3. "Regarding the material" is not clear enough. They may sell many things to you. I don't know what a "water shop" is.
4. I don't know what MTC is. I don't know if it's countable or not. I can't help you rewrite this without knowing this.
Not knowing what you really want to say, I've tried my best anyway:
Dear Sir or Madam,
Regarding the materials we are obtaining from you for the [better name of project], I am requesting that future shipments include the MTC for all items. If you don't have the MTC for all materials, please let me know which materials this applies to and when you'll be able to receive them.
Thank you very much for your assistance in this matter.