Scanned Mail

You know how banks (with good online systems) scan your checks when they are deposited, and allow you to view them online to keep track of what's what?

You should be able to register an email address with the USPS or have online accounts. Then they should scan outgoing mail as soon as it's received and routed, and send you or post for you a picture of the mail that is coming to you. That way you can know if, say, a client has sent a check when they say they have. Or your landlord will know that a check is on the way. Or the IRS knows that you have sent your taxes in on time.