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 an additional minutes 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)

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)

Dear sir/madam:
[organization] would very much like to have someone from your company speak at our conference on [topic].