I know some people have in-boxes with thousands of emails, so much so that at A&A we even have an inbox archive feature that files them away by month.
I do not - my inbox is a TODO list (ok, saying TODO not "to do" is down to so much use of vim and it highlighting of "TODO" as a keyword, sorry).
My level of stress is directly correlated to the number of items in my inbox. They are the urgent and occasionally important items in my life.
For those that have never been on a time management course (thanks, STC), "urgent" and "important" are two independent attributes. You can have unimportant urgent tasks and important but non urgent tasks. The later tend to change over time and become urgent eventually.
My inbox is is urgent and important, and if still there it is "big".
If not important then the email can be deleted if busy, that is really what non-important means (you can live without doing it). Usually I reply to such emails "too busy" or some such and delete it.
Non urgent, well, they are not nice. I tend to make some diary entry for them and delete the email.
But some things are both important and urgent.
But consider a third metric, not really on the course I did, "big"!
The amount of work involved in handling the issue. If very small, then FFS "just do it" now and get it out of the way regardless of important or urgent. Much of my inbox is a reply - a viewpoint, an opinion, or better still a delegation... It is done and dusted in seconds. I don't even have to consider important or urgent!
But when I have a big task, that is urgent, and important, that hangs around in my inbox, taunting me... It adds to my stress. I can't "just do it" as it will take hours of concentration, but I cannot just "schedule" it as it needs to be done soon, now even.
So, right now, I am happy. Yes there are many things to do, but none are urgent, important and big so none are occupying my inbox.
My inbox is empty and I am at peace with the world....
[not for long]