Hi guys I just joined a new company in IT department, and now I have to cantact with the BT director in our business department. So I have to write a hello letter and get started role.
Is there any suggestion or sample letter for this situation.
Best regards,

What will your duties be? Have you started writing yet?

As the main project is in UAT, there going to be some new business needs from BT.
My duty at this moment is to transfer the business needs to IT requirements, and may need to arrange develop meeting to get the IT　solution.

Acturally, our GM already introduce me to BT team and send my resume to the director

Why don't YOU write the letter as best you can, then post it (but don't put in the company or personal names), and I will correct grammar and spelling and make it sound good? Okay?

Hi xxx,

I am xxx, the... in... of.. I am glad that I may have chance to work with you.
If you have any question, or anythiing I can do for you, just feel free to contact me.

Best regards,

Not enough.

I would also give a short personal background of your qualifications, how long you have been doing this and that you are available for a Q & A.

Stringer

The BT team already arranged a meeting with our GM and discussed how I can join the flow. They already know who I am what I can do.
So I just need to say hello and ask to take over their requiement

So all you need is a two-sentence letter?

Maybe others, but not the background some.
I need it in formal way.

I need more information than what you are giving me. I'm not sure what you need.