Follow the steps below to create forwarding accounts that can send E-mails to multiple destinations.
Create a mailbox or forwarding E-mail account and set up the additional forwards that will receive the incoming E-mails. E-mail accounts can forward messages to a maximum of two additional addresses.
Log in to your 1&1 Control Panel and select the relevant package.
Click the Manage E-mail Addresses link from the Mail panel.
Manage E-mail Addresses
Click the Set up forwards link from the Further options menu.
Further options menu
Under E-mail Account, enter the E-mail address and click on Add.
Enter the additional address to which you would like to forward incoming messages. To add more forwards, simply repeat the process. Save the changes by selecting OK.
Forwards to be added
For additional information, you may want to reference: