Autodiscover is a feature that 1&1 has enabled for our mail service, that allows you to setup your e-mail account by only supplying your e-mail address and password.
Because 1&1 has the autodiscover feature enabled, your e-mail client (such as Microsoft Outlook) should use your e-mail address and password to automatically detect the correct e-mail settings and complete the setup of your e-mail account, without you having to manually enter the rest of the settings.
Additionally, you have the option of creating your own autodiscover record by creating an "autodiscover" subdomain and adding an A record to overwrite 1&1's default record.
If you are presented with a prompt that asks you if you trust the URL:
Please click the Allow button. You may also tick the box so that you are not prompted again in the future. This will ensure that the rest of your e-mail settings are automatically downloaded and configured for you.