Dearsir/madam:
I’mdelightedyouhaveacceptedourinvitationtospeakattheConferencein[city]on[date].
Asweagreed,you’llbespeakingonthetopic"XX"from[time]to[time].Therewillbeanadditionalminutesforquestions.
Wouldyoupleasetellmewhatkindofaudio-visualequipmentyou’llneed.Ifyoucouldletmeknowyourspecificrequirementsby[date],I’llhaveplentyoftimetomakesurethatthehotelprovidesyouwithwhatyouneed.
Thankyouagainforagreeingtospeak.Ilookforwardtohearingfromyou.
Sincerelyyours,
[name]