Personally, my inbox is my TODO list. One of them, anyway. I also use Things as my TODO machine. That seems messy, doesn’t it? But it seems to work for me.
The reason is that my TODO list isn’t all email-related things. It could be “buy a gift for my nephew’s birthday” or “make an appointment to get a new driver’s license”. That’s my master list where nearly every important TODO ultimately makes it.
But the emails sitting in my inbox are often essentially TODOs as well. In the form of “edit this article so I can respond with next steps” or “answer this person’s question but also write a draft blog post on it because it was interesting”. Those things are worthy of being on the master TODO list, but they don’t always make it there. Usually, they feel fine sitting in the inbox for a while, because I know I’ll get to them there as well. Moving them feels like unnecessary busy work. It doesn’t always feel messy to me, it feels like a working system.
But sometimes I will yank long-sitting emails off the inbox. I’ll write them up, like the examples above, and plop them into the master list. Sometimes I just feel like hitting “Inbox Zero”, and I know it’s going to take me a little while (days, weeks) to get to that thing and that is too long to sit in an inbox for me. That busy work of moving TODOs from one place to another is exactly what I don’t like about real Inbox Zero.
I don’t mind alternate TODO lists. For me, for now, it’s fine.