When "selecting all" within Gmail, an option pops up to select the remaining xxxx number of emails from the rest of the pages automatically. In Missive, however, when hitting Cmd+A it only selects the preloaded threads. The only way to actually select all threads within a given label (in order to mass delete or mass re-label) one would have to scroll all the way down first in order for everything to preload, and then hit Cmd+A. It works, but it's very painful to do with really large folders.