Dear
Please allow me to take this opportunity to express my heartfelt thanks to you for your contribution to our recent conference in __(location)__. Members of our executive board have also asked me to pass along their sincere appreciation for your participation in support of __(type of cause)__.
We’ve received numerous positive comments about your presentation from attendees of the conference. You certainly captured the interest of your audience with both your skilled speaking abilities and the in-depth knowledge you possess on the topic of __(topic)__. So much so, in fact, that we’ve even received requests for a copy of your presentation. It appears that you were a real hit with this audience, __(Name)__.
And on a personal note, I also want to tell you how much I appreciated the time that you and I were able to spend together during the down times at the conference. Our professional and personal discussions were most refreshing. Not only did I learn a lot about __(topic)__ from you, but I genuinely enjoyed your company.
Once again, thank you for your tremendous contribution to this conference. There is no doubt in my mind that it would not have been the success that it was without your enthusiastic participation.
Sincerely,