英文书信-无法生产

Dear XXX,

Thank you for your enquiring.(一定要在信的开头道谢，这是礼仪)

I'm sorry that my company can't produce such products.（可以简短的说明原因）

However, pls give me a chance to introduce our products and servise in short.......（可以顺带简单地介绍一下自己公司的产品和服务。或是说说不能提供这种产品，但是否可以提供相关服务）

Thanks & Best regards,
yours sincerely,
XXX
(company name and contact information)

Dear xxxxx,

Thank you very much for your e-mail .Sorry to say we cannot produce this kind of products.

Best regards.
xxxxx