Mailplane 3.6.2
Uncomplex has released Mailplane 3.6.2, upping the system requirement for the Gmail-specific email client to OS X 10.10 Yosemite or later. The update also fixes issues with Google Inbox (with the notifier now opening an existing Google Inbox tab instead of Gmail), adds a Reply All button to the separate compose window toolbar, updates WebKit to the same version used in Safari 9.0.3, and switches its update feed to HTTPS. ($24.95 new, free update, 23.1 MB, release notes, 10.10+)
If Google Inbox catches up with Mailplane, life will indeed be grand.