How are e-mails being filtered?
E-mails are passing through a system of static, dynamic and self-learning filters and rule types, which are reliably detecting Spam. Filtering takes place in two steps. The first step takes care of those messages that – with the highest probability possible – are obviously Spam. In these cases our systems break the connection with the sending server giving an error message and a reason. The vast majority of incoming mails (currently > 99%) is actually being blocked this way and not transmitted to quarantine. False positive rate at this point is extremely low at less than 1 per 1 billion mails. In the second step, senders, subject, text, links and attachments in the mail are analyzed automatically and rated. If the rating variable exceeds a certain value, the E-Mail will be put into quarantine and can still be retrieved manually.
