Connecting your inbox is totally optional. It’s only required to enable features that require monitoring or analysis of your email when you are not there (ex: response detection)
To broker this connection, we use a 3rd party (Context.io) – a company that specializes in doing exactly this. Working with them allows us to build functionality, while keeping the storage and handling of your email content to a minimum. FollowUpThen uses only header information from your emails and will never programmatically open or store use the actual email content from any of your emails that are fetched through this direct connection (even including the ones where there is a followup scheduled).
Context.IO uses non-personally identifiable information about your email to provide aggregate email intelligence, email fraud-protection and more. Read more about Context.IO and Return Path (their parent company).