UPDATE: It's been my favorite mail client for years  it usually just works once you've set up everything. Perfect for IMAP. Though  with Android 6 you have to manually exclude K-9 from battery optimization  else it will stop receiving new mails. However: Ever since a recent major update  they changed parts of the GUI. In message view  attachments are now displayed at the very bottom. You have to scroll aaaaaaall the way down to even notice attachments. So easy to overlook  and to accidentally delete a billing mail because the first few lines looked like every other spam email. What were they thinking?? Give us an option to switch this back!
February 17 2017