Dear Mr. Smith,
I am writing to you just to tell you how much I appreciate the warm welcome you extended to my colleague Ms. Jenny Wilson when she visited your company last week.
The help and advice you gave her, and the introductions you arranged for her,
have resulted in a number of very useful meetings. I should like you to know how grateful I am for all you have done to make them possible.
I realized the value of time to a busy person like you, and this makes me all the more appreciative of the time you so generously gave her.