Thank you so much for …
I warmly appreciate your hospitality.
I am writing to express my thanks for …
I am writing to extend my sincere gratitude/appreciation for …
I would like to convey in this letter my heartfelt thanks to you for …
Thank you very much for the gift you sent me. It’s one of the most wonderful gifts I got on my birthday.
I am writing this letter to thank you for your warm hospitality accorded to me and my delegation during our recent visit to your beautiful country. I would also like to thank you for your interesting discussion with me which I have found very informative and useful.
Again, I would like to express my warm thanks to you! Please accept my gratitude.
Thanks again and I hope that I will have the opportunity to return/ repay your kindness.
I am looking forward to…