Chad Dickerson on email management at a new job (emphasis mine):
[I'm] cleaning out my e-mail inbox, and it's a mess. Only 22 weeks into my job at Yahoo!, I'm looking at an inbox with 5100+ e-mails, since I have deleted absolutely nothing since I started — and that leads to the point I want to make about getting organized in a new job. It might be GTD heresy, but in a new job, I think you should let your inbox fill up for the first 4–6 months… Then, 4–6 months later, when you've really begun to make sense of your role, the organization, and how it all works, spend a few days churning through that old inbox and doing some filing.
That's what I'm doing, and I'm finding e-mails on topics that were inscrutable to me in my first couple of months, but are now immensely valuable. I'm finding e-mails from people who I've gotten to know, but didn't know when I received the e-mails. I'm finding informational e-mails from HR and Finance that didn't make sense when I got them, and now do. I'm finding e-mail threads about projects that were just one in an overall soup of projects, but are now very specifically pertinent to what I'm doing now.