You can follow the instructions below to transfer your domain from 1&1 to Cloudflare.
To transfer to a new registrar, your domain must meet the following requirements.
If it is listed as available for transfer in the Cloudflare dashboard, these restrictions have already been checked.
Cloudflare Registrar does not currently support email forwarding. If you require email forwarding from your registrar, you will need to use a third-party forwarding service and configure your MX record in the Cloudflare DNS setting for the domain.
Login to the 1&1 account where the domain is registered. Navigate to the Manage domains page and select the domain you plan to transfer.
Select the Registration & Transfer tab. In the section “Domain transfer lock” toggle the button to remove the registrar lock.
Below the “Domain transfer lock” section will be a row listed as “Change provider”. Click “Show Authorization Code”. The 1&1 dashboard will launch a pop-up with the code.
In the Cloudflare transfer screen, input the authorization code. Each domain will have a unique authorization code and you will need to enter each for every domain you want to transfer.
Once Cloudflare processes your transfer, 1&1 will send an email to the domain’s registrant contact (the same address where the authorization code was emailed). The email will contain a link that you can click to immediately approve and process the transfer. If you do not click the link, the transfer will automatically approve within 5 days.