Okay, first, what I want you to do is go find a big stick, the largest one you can wield. Then, go stand in front of your computer and shake that big stick at all of the promotional e-mail you receive: coupons and coupon codes, online catalogues, and invitations to increase (or decrease) the size of your genitals, waist, hips, feet, nose, or ear hair. Clearly, shaking a stick at all that received e-mail is as futile as the expression "more e-mail than you can shake a stick at" is ridiculous.
Spam filters help manage some of it, but there's a lot of this stuff you want to get. E-mail filters can help you direct it into various folders, but most e-mail applications (whether Web based or not) have a limit on how many filters you can create -- plus it's a lot of effort and not everyone is that comfortable with the technology.
So, whaddya do?
My suggestion, in this age of prolific and free e-mail accounts, is to simply create an "advertising only" e-mail address. I have one of my own (roughly named firstname.lastname@example.org) and this is the account I use for any Web based subscription service, whether it's Coldwater Creek, the Creekside Inn, or In-and-Out Burger. Everything comes to this single account and I look through it at my leisure and delete things freely, never worrying that I might delete that one terribly important e-mail from a family member. (You know the important e-mail I'm talking about. It's the one that warns against eating too many oxlips because the middle toe on your left foot could grow unreasonably large ... and be sure to forward this to everyone you know!)
Once having done this, be sure to use your "real" e-mail address only for "real" people (real people being humans rather than Web servers and grungy guys you met at the bar who you don't plan on giving your phone number to).