Heard of Mailinator? Get a mailbox at this throw-away service and anybody can read your inbox, which is exactly what the operators of the service intend.
Mailinator has a few unique twists that make it unlike other mail services you might have used. First of all, you don't have to sign up for an account. Just make up a username on the fly and pass it around to whoever you want. This works because the mail service accepts mail for any mailbox at the mailinator.com domain.
Secondly, you don't need a password to check the inbox for new messages. At the Mailinator Web site you simply enter the inbox name, click the "go" button, and presto -- you see a list of all messages waiting. This is of course means that anybody can read any mailbox they want. But that's part of the intent of the Mailinator. Mailboxes are disposable, open to anybody, require no setup and no personal information to establish, and thus require no password to access.
The company that provides the Mailinator service, Outscheme, says that Mailinator is a solution for spam. The premise is that you can make up any username you want and then give out that email address to anybody without having to worry about how that email address might be used.
When email arrives for your inbox at Mailinator, the system creates the mailbox if it doesn't already exist. If the mailbox does exist then the received message is added to the mailbox. According to information posted at the site, after "a couple of hours" the mailbox will be deleted.
Just for grins I decided to check a few inboxes to see what is in them. All I found was junk mail. That's part of the point of using the service. It helps ensure your regular mailbox doesn't become a target for spam.