We require that your member have an Office 365 Business or Google Calendar account in order to use Appointlet's scheduling system.
If you are utilizing Outlook without 365, it is possible to sync with Google Calendar using software like GSyncIt.
If you use iCal and want to use Appointlet as well, check out these guides from Google.
We are not able to connect directly with Exchange or iCloud at this time. If Google and Office 365 do not meet your needs, please write in and let us know!