Hi [Prospect Name],
I hope this email finds you well.
I'm writing to you today to propose a partnership between our two companies.
I've been following your work for a while now, and I'm really impressed with what you've accomplished. I think our companies would be a great fit for each other, and I believe that we could achieve even greater success if we worked together.
I've attached a case study that outlines a recent project that we worked on. This project was a great success, and I think it demonstrates the value that we can bring to your company.
I'd love to schedule a time to chat with you and discuss this further. I'm available [Days and Times].