re:
It's similar how a printer spools documents so if your sending multiple emails they queue up in the the outbox. The process is essentially like this
- Once the server acknowledges the request & authenticates said request
- Data is sent to the mail server from client (your tablet)
- Once the data gets sent completely it is moved to your sent items.
Basically the out box is the digital version of the out-tray (mail ready to be sent out) and the inbox the digital version of the in-tray (received mail).
In laymen terms, this how the outlook desktop app behaves and therefore the app mimics this behavior thus is completely normal.