Everyone who downloads Inky will get a free 14 day trial.  Inky recognizes the types of accounts added during the trial.  If you have a gmail.com, iCloud, or Outlook.com account you don't need to do anything else, continue to enjoy Inky for free.   

For any other type of account added (for example: Yahoo!, Microsoft Exchange, Office 365, Google Apps, and work IMAP accounts) Inky offers a subscription for a low monthly fee at https://store.inky.com.