An Authorisation Code (EPP Code) is a 8 to 32 character code assigned by the provider or host of your domain (Registrar) at the time a domain name is created or after it is transferred. The authorisation code is basically a password for transfer of the domain. Authorisation codes are an extra security measure, ensuring that only the owner of the domain can make transfers.
All .com, .net, .org, .info, .biz, .name and .us domains require an authorisation code. If you do not know your authorisation code or are getting a Authorisation Code Rejected notice, please contact your Registrar for the correct information. Once you have it, you can update the authorisation code of your domain through the 1&1 Control Panel. Please have it ready before you initiate a domain transfer.