i'm delighted that 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.
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.