Sometimes it is easier to just do whatever tasks stream at you through the incessant flow of email than to work on the conceptually difficult, important, long term research papers. At other times you want to scream and throw things at the stream of demands as you happily grapple with the kinds of question that make this a wonderful career.
Successful scientists find a balance either through great organization or great irresponsibility. You can ignore requests, or agree to them and not follow through. You can delete emails and be the person the students despair of reaching. Such people seem to thrive, even in my own department. But I don’t recommend it.
Organization requires a system. You will find one that works for you. Here are some possible elements. You can organize tasks by email or by calendar. One successful researcher I know puts tasks on her calendar on the day they are due and doesn’t touch them until then. If you organize by email, I recommend as few folders as possible, one for everything you need to do and another for everything else. You can find stuff in the general folder by searching, so you’ll need one or two others for things that you won’t know how to search for, like emails from people you don’t know, perhaps about travel, or job applicants.
This means the to-do folder will contain different kinds of tasks, from letters of recommendation to reviews, to committee tasks, to reading student papers. This stuff is part of your real job, so get to it often. But the main part of your real job doesn’t appear there. It is developing and pursuing new ideas in research and teaching and helping others to do likewise.
So keep your in-box empty and don’t dither over tasks. Get the less creative ones done at your less optimal times of day, perhaps late afternoon. Just be sure to complete them quickly when you open them or they will greedily expand the accordion of time that should be saved for thinking. Touch the smaller tasks only twice, once when they come in and you either deal with them immediately or move them to a calendar or to-do list and once when you take care of them.