What to include in an intro letter for a potential customer?

I am experienced in my field (Software Engineering) but its mostly as a worker. This means that I can handle the work and can get it done from workers but I don't exactly know how to market my skills as a company and get the projects. Now that I was considering to establish a new company of my own, luckily I was introduced, through a mutual friend, to an offshore-living person that runs his own frontend company there and gets work done from other companies that don't interact directly with the client (they work in backend).

That person told me that he has so many clients and projects available and he always get them done from backend companies of a certain country but all companies are bad in that country (according to him) and he would like to switch to another country's single backend company. Through the same friend, he asked me to send him a letter that he called as Introduction Letter. I presume I need to include my portfolio in it. What I need to know is:

• What I should include in this letter other than portfolio?
• Any links available online that could guide me about it?
• How important the order of items is?
• Should it be in highly formal style and language? (I don't have very close and personal relations even with our mutual friend).

Thanks for any help...

I've seen a lot of names for it, such as "corporate capability statement", or "corporate capability package" as I see it on wikipedia. Regardless, you want a formal document that outlines your specific areas of expertise. If it's high level project management talk about the management styles and structures you work with. If you work at the custom coding level outline the languages that you are most familiar with.

Pair that document with a portfolio, and preferably 1-3 strong client references that you did significant work for. If you don't have enough references play to that advantage when attempting a sale, letting the client know that you are getting started and need good references so you will do an excellent job for them.

Beyond that you could add a more personal letter about your vision for your company and how you see yourself partnering with the client. Do make sure to customize this letter for each client! Whether or not to add a personal level varies on the company, the client, and you. If you are the kind of person to want to have a personal introduction, include it. If that's not you, you're all business, then don't.