BERLIN — "This message will automatically self-destruct after reading." Those were the words that brought a thrill to many a spy film during the Cold War, as viewers watched agents send messages that burst into flames after viewing. And now you can do the same, at least digitally, with a new service from the website onetimesecret.com, offered by Delano Mandelbaum. The service was conceived for people who want to send passwords or other sensitive data by email that was never meant to be seen by anyone but the recipient. It's easy to use. Just type your message into the text box and click on "Create a secret link." That generates a web address that you then send to the recipient. The link can be followed once. After that, it will only lead to error messages. No account is needed to use the service, but that means messages will only be available for seven days after being sent. Those who set up an account can send secret messages that will linger unread for 30 days and also get a password for added security. The service is free.