I've read so many articles listing the reasons why you shouldn't use your inbox as a to-do list, but I've found that it works for me, and it's not just limited to people with small inboxes. I process my emails into different folders based on priority, such as "Inbox" for high-priority items, "To-Do" for tasks that aren't time-sensitive, and "Someday" for things I'm interested in but don't need to do immediately. To create labels and sublabels, I use Gmail's features, including creating filters to automatically sort emails into the right folders. Additionally, I use add-ons like Trello to move emails to other apps, save new emails matching certain traits to Google Spreadsheets, use canned responses to quickly get tasks off my list, utilize Gmail's snooze feature to minimize distractions, and star emails to isolate tasks for today into a separate list.