If inbox zero is what you're trying to achieve, this magic button
will help you do
it. Once you've responded to an email, that
conversation will be moved away
from the inbox into a digital filing
cabinet. Archiving doesn't mean deleting mail.
You can find archived
messages in the All Mail tab on the left or with the search
bar on top.
To enable Send and Archive, go to the gear icon (top right) >
Settings. Under the
General tab, find Send and Archive and select Show
Send & Archive in reply.