AXIGEN provides various types of filters at each level of mail processing that allow you to increase mail traffic security and block any type of unwanted mail messages from reaching their intended recipient mailbox. The filtering system in AXIGEN is highly effective and allows maximum flexibility in defining what email messages should be scanned, what filters should be used, the order in which these filters are applied and the actions taken according to the results of the scanning process. The filters can be applied both for incoming and for outgoing email traffic.

Filter Types

1. Message Acceptance Rules

AXIGEN implements a set of message acceptance rules at SMTP-connection level. The system administrator can configure and implement message acceptance rules and adjust them to best suit their security requirements. Incoming connections established via SMTP and the message flow can be easily managed using the established rules. Moreover, they allow adding headers, changing addresses and other such actions. For more details, see the Message acceptance rules section.

2. Routing Rules

To further fin-tune email communication management at SMTP level, AXIGEN Mail Server implements Routing rules.

The Routing rules correspond to the Processing and SMTP Outgoing modules and enable administrators to define the NDR (Non-Delivery Receipt) text and the conditions when such a message is returned. The system administrator can also customize SMTP Outgoing actions for all or part of the relayed email communication. For further information, see the dedicated section in this chapter.

Important! The following filter types are defined in the WebAdmin interface and in the configuration file:
type script - for Message rules
type socket - for Antivirus/Antispam rules

3. Message rules

Message rules instruct the AXIGEN Mail Server to take certain actions on processed email messages based on pieces of information contained by the message headers.

Using Message rules is safe since they do not operate on the mail content but only extract information from the mail header and take actions according to the pre-defined rules. See the Message rules section for further details.

4. Antivirus / Antispam Filters

Antivirus / Antispam Filters can be easily used with the AXIGEN Mail Server to ensure a high security level for email communication. Commercial Antivirus applications can communicate with AXIGEN either directly (using the AXIMilter module) or through AMAVIS. For more details, see the corresponding section of the current chapter.

This type of filtering allows integration with virtually any third party applications, including Antivirus and Antispam applications. Currently, connectors for ClamAv Antivirus and SpamAssassin Anti-spam application (both open source) are implemented ensuring effective virus and spam protection for all mail traffic managed by AXIGEN Mail Server.

Moreover, AXIGEN supports integration with Amavis, a generic interface used to connect a mail server to twelve different Antivirus applications: KAV(Kaspersky) for Mail Servers, BitDefender, Sophos, F-Prot, DrWeb, Symantec, F-Secure, Avast, eTrust, Norman, Panda and McAfee.

To see instructiuns on how to make AXIGEN work with ClamAV, see the corresponding AXIGEN forum posting. For SpamAssassin, you simply need to install the application, no further configurations are necessary. A sample setup procedure for connecting these two applications to AXIGEN is also given in the AXIGEN Install and Config Guide.

For instructions on setting up the AXIGEN Mail Server integration with Amavis, see the dedicated article on the AXIGEN site. At this time the integration has been tested for Kaspersky and BitDefender but the procedure is similar for any of the products supported by Amavis.

Active Filters

Filter configuration in AXIGEN, also involves the notion of Active Filters. Although not a distinct filter category, the Active Filters designation is used to refer to filters currently enabled in AXIGEN. This designation is particularly useful when enabling filters.

Filtering Levels

In AXIGEN, you can apply filters at three levels:

server level (these filters are applied to all emails directed to any account / mail list from the server)
domain level (these filters are applied to all emails directed to the domain to which the account / mail list belongs)
account / mail list level (these filters are applied only to the account / mail list for which the filters have been created)

Thus, a typical filtering chain in AXIGEN will contain different types of filters, applied on different levels.

If one of the filters in the filtering chain yields an error (internal error, AFSL or any type of error), the email being processed is kept in the processing queue and it will go through the filtering chain all over again, at a later time until all the filters in the chain can be applied.
If all the filters in the filtering chain yield a PASS action, and the last one yields REJECT, the email is rejected. In case one of the filters situated in the middle of the chain triggers a REJECT or DISCARD action, the email will go through the filtering chain again.

The order in which these filters will be applied, is based on their level and on their priority. See Activating Filters for details on activation inheritance and priority levels.

AXIGEN Mail Servers can easily integrate with other third party applications through a simple interface which is made available as part of SDK (Software Development Kit). For more details on SDK delivery, please contact the AXIGEN Sales Department.

See subsections of current page for more details:

Message Acceptance Rules
Routing Rules
Antivirus / Antispam Filters
Message Rules
The AXIGEN Filtering Module
Activating and Prioritising Filters and Rules
Language Specifications for Policy Configuration