英文感谢信开头段常用句式

I would like to convey in this letter my heartfelt thanks to you for...

I am writing to extend my sincere gratitude for... I am writing to express my thanks for...

I feel deeply indebted to you and I really dont know how to thank you enough for your help.

I must thank you again for your generous help. I am most grateful for your selfless donation. My true gratitude is beyond the words description. I feel most obliged to thank you once more. Please accept my gratitude, now and always.

I am writing to show my sincere appreciation for...