信的格式化結語

I greatly appreciate your help.

I hope to hear from you soon.

We very much look forward to your participation in this worthwhile activity....

I also enclose the ... for your reference.

牛津詞典:

I would be grateful if you could send the completed form back as soon as possible.I would be most grateful if you would keep this matter confidential.

http://oald8.oxfordlearnersdictionaries.com/dictionary/grateful

Please do not hesitate to contact.... at ...(email) or on (telephone)

 I am more than happy to be of asistance." or "I am happy to be of assistance."
It means 'More than happy' means 'very, very happy', 'ecstatic'.