1) It is with the greatest pleasure that I write to cordially invite you to attend the meeting.
2) It gives me the greatest pleasure to invite you to visit this exhibition.
3) It is very kind of you to ask us to dinner this coming Saturday evening. But, to our deep regret, we cannot accept it.
4．3 批评、投诉信
1) I am writing to complain about….
2) I think it’s high time you realized…(我认为是你认识到……的时候了).
3) I must warn you that unless you do something about the situation I will be forced to take legal avtion.
4) To be frank, I am not prepared to put up with the situation any more.
4．4 感谢信
1) I warmly appreciate your hospitality.
2) I don’t know how to thank you for your kindness to me.
3) I am writing to thank you, on behalf of my wife and on my own behalf, for the lovely time we had at your party last night.
4．5 推荐信
1) I am very pleased to write this letter of recommendation to support his application.
2) I am very delighted to have been asked to write this letter of recommendation for…
3) Aside from the aspect of…,he gives me the impression that…. (建议：英语作文)