public class ExchangeFunctions
{
	private const string _username = "uname";
	private const string _password = "password";
	private const string _domain = "domain";

	public static string CreateAppointment(string mailboxId, MyAppointment appt)
	{
		var service = new ExchangeService(ExchangeVersion.Exchange2007_SP1);
		service.Credentials = new WebCredentials(_username, _password, _domain);

		// auto loads the url for the targetted mailbox
		service.AutodiscoverUrl(mailboxId);

		var appointment = ConvertAppointment(service, appt);

		// save the appointment, bound to the targetted user's mailbox, using delegate permissions
		appointment.Save(new FolderId(WellKnownFolderName.Calendar, mailboxId));
	}

	// Convert My Appointment to Exchange Appointment class
	private Appointment ConvertAppointment(ExchangeService service, MyAppointment appt)
	{
		// create the appointment
		var appointment = new Appointment(service);
		appointment.Subject = appt.Subject;
		appointment.Body = appt.Body;
		appointment.Start = appt.Begin;
		appointment.End = appt.End;
		appointment.LegacyFreeBusyStatus = appt.Busy ? LegacyFreeBusyStatus.Busy : LegacyFreeBusyStatus.Free;

		return appointment;
	}
}