Learn how to change the password of your e-mail account through 1&1 WebMail.
In order to complete this process, you will need to know the current e-mail password. If you have lost or forgotten an e-mail account's password, the 1&1 account owner will need to Reset the E-mail Account Password through the 1&1 Control Panel.
First, log into the 1&1 WebMail interface at http://email.1and1.com/ using your full 1&1 e-mail address as the username and the account's password.
Click the Configuration gear icon toward the top-right of the page and select Edit Settings.
Check the Advanced Settings box.
Click Change Password from the advanced settings page.
Enter the current or old password once and then the new password twice to confirm that they match. Then click the Change Password button.
For additional information, you may want to reference: