It may sound counter-intuitive, but having multiple email addresses will actually cut the clutter in your email inbox.
You should have at least two email accounts: one for your personal email and one for when you are asked to provide an email to sign up for something. You are much more likely to get spam email from signing up for something online than you are from your family and friends. You can safely ignore most everything that goes to that email account.
You should also have a professional email account for any work or volunteering you do. That way you aren’t likely to lose important communications because they are mixed in with updates from your family or jokes from your friends.
Your Second Life avatar may need his or her own email as well. That’s helpful if you are keeping SL separate from RL. If you have a virtual business, it is also helpful to use a separate email for your avatar.
Keeping separate the various types of email messages you may get is much simpler when they go into separate email accounts.