Target Skills:

Ability to describe the different levels of message filtering.

Ability to describe questions to ask before setting up filtering.
 


 
 
 

More info:

Message Filtering with UBE (Admin Guide)

Setting up Message Filtering

The Messaging Server gives you great flexibility in filtering messages.  We'll discuss the different levels of filtering, questions to ask before filtering, and then cover the built in UBE (Unsolicited Bulk Email) filter available through the Console.
 

Different Levels of Filtering

There are basically 3 places you can do filtering on messages as they move through the SMTP process:
1. TCP Level 
Referred to as TCP-Wrappers, these filter before the SMTP connection is made. The allow/deny filters for smtp services discussed in the Security Module are an example.
2. Pre-SMTP Accept
Referred to a Protocol-Level plugins, these filter before the messaging server accepts the message into the queue on disk.  The Anti Relay plugin that ships with the product is an example.
3. Post-SMTP Accept
These filter after the message is in the queue on disk.  The UBE plugin that ships with the product is an example of this.

Questions to Ask Before Filtering

Questions you need to ask yourself before setting up filtering are:
1. Do you really need to filter messages? 
Filtering consumes system resources, it can be difficult to precisely define the characteristics of all unwanted messages, and you run the risk of rejecting desirable messages.
2. What are the characteristics of the messages you want to filter?
3. At what level do you want to filter?
Perhaps the best way to filter is at the protocol level, so you don't waste your queue resources, but you have to write your own plugin. 

The post-SMTP Accept level may be most desirable, even though it consumes your queue resources, since the UBE filter plugin is already developed and has a convenient GUI from the Console.

     

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