When asked about annoying spots on the computer, most people mention the email in-box. They fill quickly with career-critical information, copies of newsletters, and videos of cats. Usually, no one sees that pile (unlike the in-box on your desk,) so it is pretty easy to just let it go, and grow, and before you know it, the thousand emails seem like a mountain to get rid of.
Here’s a great article, with a bit of an advertisement, but useful information:
A hint for when you start deleting: if you temporarily organize them by sender, it will be easier to sort the important (from the boss) from the trash (newsletters.)