What is the Auth-code? How do I obtain it?
The Auth-Code, also known as Auth-Info or EEP code, is a password assigned by the registrar as a required security measure when requesting a transfer for domains of most of the extensions. Not all extensions (TLD) require an AuthCode to be transferred, for example, the .ES domains no not have this authorization code.
If you do not have it, you should request it from your current registrar/provider, who will tell you what to do to obtain it. This password is mandatory and necessary in order to request the transfer of your domain.
For domains registerd with MrDomain, you can get the Authcode of the domains on the "Settings" box of the "Summary" section of the domain's management page of your customer area: