Dear Sir,
In reference to our discussion of January 5, the package of diskettes you sent arrived today in good condition. I have copied and quickly viewed the files, and everything seems to be in order. I'll get to work immediately. As soon as I have something to report, I'll call you at work.
Thanks for giving me the opportunity to help. I'm excited about this project and feel a lot of good will come from it.
Yours Truly,
[Your Name]
