Spam Protection

Astaro's Spam Protection (Spam Filter) scans inbound email messages (SMTP and POP3 protocols). It performs a series of tests and assigns a "spam score" to each message indicating the probability that the message is unsolicited.

Messages whose score exceeds thresholds set by the administrator are dropped, returned to the sender, passed to the recipient with a warning, or quarantined.

Accurate Identification of Spam
Astaro?s Spam filter utilizes multiple methods to pierce the disguises used by professional spammers:

• Sender Address Verification, Greylisting, BATV reverse path signing, and SPF record checking. Messages are tested to determine if they come from legitimate email servers.

• Realtime Blackhole Lists (RBLs). Email addresses are checked against databases of known spammers.

• Header Analysis. The header section of emails are checked for false or altered information and addresses with invalid characters (such as !, %, /, |)

• Body Analysis (Heuristics). Words and word patterns typical of spam are identified.

• Whitelist and Blacklist. The administrator can list email sources known to be legitimate and illegitimate.

Management Control
Administrators can tune Astaro?s spam filter to balance stringent blocking against the risk of missing legitimate messages. Options include:

• Enabling or disabling tests.

• Creating local whitelists and blacklists.

• Taking actions based on "spam score" thresholds.

• Specifying that suspect messages should be:

• Dropped
• Rejected and error notice returned to the sender
• Passed through to the recipient with a warning
• Quarantined for later evaluation and disposition

Performance and Simplicity
Astaro?s spam filter is integrated with the firewall and anti-virus. This improves performance and simplifies ongoing management:

• Performing spam testing, virus scanning and packet filtering on the same system eliminates delays vectoring files to separate systems.

• Local whitelists, blacklists and network configurations can be entered just once and shared by all of Astaro's security applications.    

• Reports track statistics on email messages processed, their size and spam score, and the number of viruses found.

Working with the Email Server
Astaro?s spam filter can add headers to email messages so that a recipient email application can take specific actions, such as sending suspicious email messages to a "spam" folder on an email user's desktop. Information added to email headers can include:

• A spam flag

• The "spam score"

• Expression match (flag that the message contains suspicious text)

• RBL warning (flag that the message comes from a domain identified in a Realtime Blackhole List)

• Users can be sent a summary of email messages addressed to them that were placed into quarantine, giving them a chance to retrieve any legitimate messages that might have been blocked.