Like junk mail in your mailbox, spam is unwanted or unsolicited email. Spam filters catch spam before it reaches your inbox. You can define the level of spam filtering in your 1&1 administrative control panel.
Choose from four levels of spam protection: off, low, middle, or high
When you receive an email, it is categorized according to the level of protection you choose. The spam filter checks the email header for things like forged outlook clients, inconsistent dates, the dollar sign ($) in the subject line, etc. Depending on the content, values are assigned to each of these indicators. For example, the dollar sign ($) is a strong indicator for spam and has a value of one point. The more spam indicators the mail shows, the more points it assigned. The email is then marked by adding "SPAM" to the subject line. You can also define other filter rules in your
local email client to sort the emails into corresponding folders right away.