Dear …
As part of __(organization’s)__ marketing strategy this year, we will be hosting a __(type of seminar)__ seminar on __(date)__. This seminar will be offered free of charge, to __(briefly describe who the individuals are that will receive and invitation)__ as a means of capturing their interest as potential clients in the future. The topics that will be included in the seminar are __(briefly list the topics)__.
We have given considerable thought to choosing a keynote speaker for this event. We need someone who is both willing to donate their time and has the ability to turn this event into a great success. Your name keeps rising to the top of our list, __(name)__. As one of the leading __(name of position i.e. Lawyers/Tax Accountants/etc.)__ in our __(community/firm/etc)__, we would be proud to engage you as the host of this __(type of seminar)__seminar. Not only are you a gifted speaker who can easily hold the interest of your audience, but your __(experience/expertise)__ in all the topic areas would add great authenticity to the seminar.
We would be very grateful to you if you would accept our invitation to host our __(type of seminar)__ seminar on __(date)__ as our keynote speaker. An event such as this, offers the potential to both you and __(name of organization)__ to gain higher recognition in the community. We thank you in advance for considering this request.
Please let me know by __(date)__, if you will accept our invitation. You may contact me at __(Phone #)__. I look forward to hearing from you soon.
Sincerely,