With thanks to www.sanebox.com and https://mailstrom.co/ I went from an email inbox of 2563 to zero in one week.
My process prior to Inbox Zero was to read an email and deal with it or mark as unread again if not dealt with. Therefore my inbox was effectively an archive. However, when I got over 67% of my 25GB Google mail space I calculated that I had a couple of years before I filled the thing up.
I am not a natural hoarder but the process was how things went for 5 years simply because some emails cannot be dealt with immediately. Someone has dumped a task on me that awaits third party action and that cannot happen until, for example, the new tax year. Enter Sanebox...
Sanebox sets up a series of customisable folders in Gmail that allows you to move mail out of inbox into, in my case, 1 day, 3 days, 1 week, Monday, 4 weeks. The message then is out of your mind until it pops up again at the allocated time. Brilliant.
As mail comes in 90% of it piles up in SaneLater and only the 20 or so vital daily emails sit in my Inbox. From there like a good GTD/Getting Things Done student I delete (# shortcut in Gmail) or archive (y shortcut in Gmail), delegate, do or defer (move to Sanebox folder).
The do phase is split into two. If a quick job (less than 2 mins) I will complete and archive (to "All Mail" in Gmail) if it takes longer I will leave in my inbox to get done when a block of time is available. The key thing is that since less than 6-7 emails sit in my inbox at any one time I know it will get done. Unlike before where unread messages could get buried off-page very easily.
Mailstrom is a tool that sifts your inbox by header and ranks top contacts, key subjects, etc. But I used if for initially was to rank all my largest emails by size. With an hour of pruning done I am back to under 60% of my storage limit.