Regarding “ethically sourced contacts”. Scailer finds an avatar and social profile links (linkedin, facebook) of a particular contact in the internet using the FullContact service as a data source. Scailer shows avatars of contacts in the left panel. That feature improves Scailer’s user experience. “Ethically” means that Scailer uses only public information: public avatars and public social profile links, and Scailer does not share that information to 3d-parties, and does not use it for advertisement. Scailer caches contact information retrieved from FullContact because of FullContact recommendation. Scailer does not store on any servers any link between email address of user and requested contact. You can find FullContact’s privacy policy here: https://www.fullcontact.com/privacy/privacy-policy/
Of course no messages are passed to the server. Scailer connects to a IMAP server (gmail, office365) using a secure channel and stores message cache in local encrypted database. It allows Scailer to work with old messages in offline mode as well as support other features like fast searching, message threading and others which improve Scailer's user experience, and at same time increase the application security. Due to strong encryption nobody will be able to read your data on your hard drive, for example if you lost it.