1) 請對方來發表一個speech，這封信是要感謝對方，同時確認對方對技術裝置的具體要求。
Dear Sir/Madam,
I'm delighted you have accepted our invitation to speak at the conference in [city] on [date].
As we agreed, you'll be speaking on the topic " " from [time] to [time]. There will be some time for questions.
Would you please tell me what kind of audio-visual equipment you'll need? If you could let me know your specific requirements by [date], I'll have plenty of time to make sure that the hotel provides you with what you need.
Thank you again for agreeing to speak. I look forward to hearing from you.
Sincerely yours,
[name]
[title]
2) 這封信則是請對方來參加自己公司的`一個招待會。
Dear Sir/Madam,
Thank you for your letter of [date]. I'm glad that you are also going to [place] next month. It would be a great pleasure to meet you at the [exhibition/trade fair].
Our company is having a reception at [hotel] on the evening of [date] and I would be very pleased if you could attend.
I look forward to hearing from you soon.
Yours sincerely,
[name]
[title]
3) 這封信是邀請對方公司派人來做介紹。
Dear Sir/Madam,
[Organization] would very much like to have someone from your company speak at our conference on [topic].
As you may be aware, the mission of our association is promotion. Many of our members are interested in the achievements your company has made.