Thank you, Mr. Gibson. I feel deeply indebted to you and I really don't know how to thank you enough for your help.It's a great honor to be following in your footsteps as Overseas Sales Manager.

　　To be honest, this promotion came as quite a surprise. I'd like to think it's mainly a recognition of the teamwork, above and beyond the call of duty, in my department. On that same note, I'd like to thank all my colleagues in the company for their enthusiasm and hard work. Due to their efforts, we've really gotten some overseas projects off the ground for Action.

　　Looking to the future, I'd still like to maintain contact with everyone, even though I'll be working at the senior level. Well, what I'm trying to say is I won't let this step-up go to my head. My door will always be open. Thank you again.

　　扩展阅读：

　　1.感谢信开头段常用句式和套话

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

　　I am writing to express my thanks for...

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

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

　　I feel deeply indebted to you and I really don't know how to thank you enough for your help.

　　2.感谢信结尾段常用句式和套话

　　I must thank you again for your generous help.

　　I am most grateful for your selfless donation.

　　My true gratitude is beyond the word's description.

　　I feel most obliged to thank you once more.