以下是一些感谢信英语作文的万能句型开头：
1. I am writing to express my sincere gratitude for...
我写信是为了表达我对......的真诚感谢。
2. I am truly thankful for...
我非常感谢......
3. I would like to extend my heartfelt appreciation to...
我想对......表示衷心的感谢。
4. I would like to convey my deepest thanks to...
我想对......表示最深切的感谢。
5. I am writing this letter to show my deep appreciation for...
我写这封信是为了表达我对......深深的感谢之情。
6. Words cannot fully express my gratitude for...
言语无法完全表达我对......的感激之情。
7. I am extremely grateful for...
我对......感激不尽。
8. I am writing to express my heartfelt thanks for...
我写信是为了表达我对......的衷心感谢。
9. I wanted to take a moment to express my gratitude for...
我想抽出一点时间表达我对......的感激之情。
10. I am writing to you today to express my sincere appreciation for...
今天我写信给您，表达我对......的真诚感谢。
希望以上句型能为您的感谢信作文打开写作思路，祝您成功！
除此之外，还有：
1. I am writing to express my deepest gratitude for...
2. I am immensely grateful for...
3. I would like to extend my heartfelt thanks for...
4. I am writing this letter to convey my sincere appreciation for...
5. I would like to take this opportunity to express my gratitude for...
6. I cannot thank you enough for...
7. It is with great appreciation that I am writing to thank you for...
8. I am extremely thankful for...
9. I wanted to take the time to express my gratitude for...
10. Words cannot express how grateful I am for...
请根据具体情况选择合适的句子开头。