Yes, this is a mandatory email that is sent out to validate your email address. For more information on this, please see this page.
This is because you are not logging into a handle that is attached to a domain, or the domain has been deleted. For a solution see this page.
You are logged in under the wrong handle. For more on this see "Insufficient rights" (Cannot see/modify my domain, e-mail address, invoice, etc)
In 2006, our website changed from version 1 to version 2. Prior to v2, we only displayed three handles on our website (the administrative, technical, and billing contacts). The owner information was registered and stored in our database, though it was not an “active” handle as such.
Then, once we went to v2 in 2006, we generated the owner handle from the information we had in our database for the owner of the domain name. It is likely that this is where the owner handle on your domain came from, and why it is unfamiliar to you. (Another possibility is that you transferred your domain to Gandi under our old transfer system, where a new owner handle was created from the whois information. More about that can be found here: How can I change the owner's email address as the admin contact?)
You can reset the password for this handle via our website at http://www.gandi.net/login/lost
Also, if you do not wish to use this handle, you can simply change the owner of your domain name from this one to a handle that you are more familiar with (such as your administrative contact handle). You may find our ownership change procedures described in detail here: Changing the owner of a domain
If you no longer have access to the email address of that handle, you will need to send in the email change form via fax or postal mail.
It is not possible to hide your nic in the whois database, though the degrees to which this is applied depends on the rules of the particular extension. But for the gTLDs (.com, .net, .info, etc.) this is not possible.
Gandi does provide a limited whois privacy service, however. More on this can be found here.
You are using a privacy or anti-spam feature. For more on this see Anti-spam (email obfuscation in the Whois)