IANAL but a software developer so I don't know how well this translates to your profession, but here goes nothing. I've handled persistent volumes of 200 mails

IANAL but a software developer so I don't know how well this translates to your profession, but here goes nothing. I've handled persistent volumes of 200 mails per day just fine using something like GTD / inbox zero. The volume of mails is not the critical part, it's the work that the mails represent. The key part for me was realizing that e-mail is just a way of funneling work into my todo list, and that I can only have a single todo list. It's not possible to do two things at once, so it's not possible to have a list of work to complete that cannot be ordered sequentially. You therefore don't need lots of lists, you just need one list that is well-tended. I keep an eye on the work ahead to proactively take steps to curate my todo list and to gather information, but once I get to work I focus entirely on the top task. I scan e-mails a few times a day. Anything that can be handled quickly is done immediately. Everything else either is put on the todo list or it is returned to sender. The todo list is a useful tool for refusing work because it helps identify what work gets moved back if the new priority gets put on top. Every mail is touched once (with the exception of replies that result from todo items). Once processed the mails are marked as read and no longer need any actions. I have no folders aside from my inbox and sent folders. I do search my mail archive every once in a while, which I keep in its entirety. Lots of mails have a context, a project that they belong to. I keep a searchable digital notebook filled with all the notes for these projects. All the snippets of information flowing into my inbox through e-mail get copied over to the notebook and structured in a way that is easy to access. This does add a little bit of extra work when information enters the system, but it saves a lot of time in the long run because of the ease of access and the ability to easily add more context that isn't captured in e-mail. You may have noticed that I didn't mention specific tools and applications. That's because after exploring lots of options I've found they don't matter all that much when you have a good system. Use whatever works best for you.