About Spam Blocking

System Overview

Users of 4SecureMail have access to a powerful automatic system designed to identify, quarantine and eliminate unsolicited commercial email (Spam) messages while allowing legitimate mail without causing false positives.

There are two primary anti-spam features used by the system -- the filter itself and the challenge/response feature.

The Spam Filter

4SecureMail includes an advanced network-based Spam Filter, which is a carrier-grade ISP spam detection system. User configurable options can be setup to filter spam based on user preferences.

The Spam Filter uses a combination of filter-rules and centralized black list matching to correctly identify over 90% of spam. Individual users select their own 'level' of spam tolerance. Typically the system is set up to automatically bounce 'definite' spam and allows users to decide what to do with 'suspected' spam.


The challenge/response option takes it a step further, creating a nearly 100% spam-free solution by allowing users to choose to receive messages only from known senders. Mail from unknown senders is automatically questioned to determine if the sender is a machine or a human. All mail from unknown senders is held in quarantine on the email server until the sender has confirmed that it is not spam.

Following is the path that an email message, sent to a typically configured 4SecureMail account, takes through the system before it is delivered to the users inbox:

  • A message is received by the email server and compared to external ORB database to ensure the sender is not blacklisted for sending spam email.
  • If the sender is clean, the message is then examined by the Virus Scanner.
  • The virus-free message is then passed on to the spam filter. The spam filter uses SpamAssasin, blacklist database, filtering rules and fuzzy matching to identify spam.
  • Mail that passes the Spam Filter is sent to the challenge/ response system.
  • Messages recognized as coming from known senders (user defined white list) are passed through the challenge/ response system to the user's inbox.
  • Messages received from unknown senders cause the system to automatically issue a 'challenge" by sending a reply to the sender. The challenge reply (based on a template customized by each user) politely asks the sender to verify that it is a human and not a spam robot.
  • The challenge/response system automatically quarantines the message while waiting for a confirmation reply.
  • All of the above steps occur on our email servers - total elapsed time is a few tenths of a second.
  • When the sender replies confirming the message is not spam, the message is delivered to the user, and the sender is automatically added to the white list.
  • The user can review messages held in quarantine at any time, and receives quarantine reports on a regular basis.
  • Users can import their Outlook contacts, address books or other lists into their white list, to keep friends or business associates from being challenged the first time.
  • Users can temporarily suspend the challenge/ response system when expecting a receipt or confirmation email from an automated system.

    see flow chart

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