Online: Use your personal tracking link (Example: www.1and1.com/?k_id=1234567) and enter your customer ID. When filling in the customer data, use the information provided by your friend or business partner.
You can find them in your Customer Control Panel under
More Data - More Features - Refer a Friend.
By Phone (855) 262-2888:
Call 1&1 and order directly for your friends or business partners, or let them know the phone number (and your customer ID) and they can order on their own.