Domain Filtering prevents the delivery of email to users of your system based on the domain name listed in the "From" address of incoming email. This technique of fighting SPAM (unwanted email) is difficult to use, and may result in your server rejecting legitimate email. Nonetheless, it remains as a useful tool in managing the email on your system.
For example, if the users of your system are receiving lots of unsolicited email from "firstname.lastname@example.org," you can put the domain "ispam.com" in the "Filter Domains.config" file to reject all email from ispam.com. However, be aware that this will also block any legitimate email originating from ispam.com.
The "Filter Domains.config" file contains a list of domain names that you do not want to receive email from. When used, email coming from any domain listed in this file will be returned to the sender as "undeliverable" due to a "User Not Found" error.
The format of the file is the America On Line ( AOL ) "Preferrred Mail" list. Until Deccember of 1997, it could be found at http://www.idot.aol.com/preferredmail/.
Editing the Filter Domains.config File
The Filter Domains.config file is a simple text file that you can modify with just about any text editor including "Simple Text" or BBEdit. The Filter Domains.config should be located in the server "config" folder along with "Mail Server.config" file.
Each record in the file must have the following structure.
A finished record should look like this.ISPAM.COM
After editing the file, save it, then restart Mail Server to have the changes take effect.