Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
FileCenter - Scan & organize documents with our paperless scanning management software. Perfect to organize & manage any kind of file. ✔ Try FileCenter FREE today!
Geary - Geary is an email application built for GNOME 3.
DEVONthink - DEVONtechnologies develops DEVONthink, DEVONagent, and other Mac and iOS apps for document and information management and web research.
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.
PDFKeeper - Open Source PDF Document Storage Solution