SPAM are unwanted or unsolicited E-mails that arrive in your E-mail account's mailbox. SPAM filters catch these messeges before they reaches your inbox. It is possible to enable the SPAM protection on your 1&1 E-mail account and define the level of SPAM filtering in the 1&1 Control Panel.
When you receive an E-mail, the SPAM filter determines whether the mail appears to be legitimate or not. The SPAM filter checks the E-mail header for forged outlook clients and inconsistent dates to name a few. Depending on the content, values are assigned to each of these indicators to result in a SPAM score.