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. As an example, NDR responses are sent when the specified recipient of an email message is invalid.

Routing Rules also allow system administrators to customize SMTP Outgoing actions for all or part of the relayed email communication. For example, they can

• establish a certain address where all emails from a certain domain are relayed, or
  
• specify a username/password authentication before relaying emails to a certain address.
  

Routing rules can contain any number of predefined options, thus being easily adapted to various security requirements.

The rules are defined using an AXIGEN proprietary scripting language and are at this time contained, along with the Message acceptance rules scripts in a single file per installed server. They can also be created automatically via the WebAdmin Wizard. For details on the options available in the WebAdmin Wizard, please see the corresponding section.

A wide range of event handlers associated with the SMTP events are available, along with various methods, message headers, envelopes and peer information are available when defining Routing rules. 

The events defined for the Routing rules and their contexts are as follows:

Event	Context
onRelay	SMTP Outgoing
onDeliveryFailure	Processing
onTemporaryDeliveryFailure	Processing

For a detailed description of the scripting language the rules are based on, please see the Language Specifications section.