If you have the SMTP (e-mail) server running on your iSeries / AS400, you may have had the
misfortune of learning about third party relay spammers. These are people who use your e-mail
server to deliver their spam. Not only will this overload your server, it will inevitably get
your domain listed as one that sends spam. With release V4R4, OS/400 provides a way to prevent
third party relay of mail. V4R3 has a PTF for this.
The method to do this involves defining the TCP/IP addresses that may send e-mail on your
server. In my case, it is the specific address of my AS/400. In your case, it may include
everyone on your network.
Create a source physical file in library QUSRSYS named QTMSADRLST. The file must be created
with CCSID value set to "500".
Start PDM on this new source file and create a new member named ACCEPTRLY. For each IP address
that should be able to send e-mail, you add a line to this file member. Each line will contain
an IP address and an address mask.
I use an entry like this:
66.12.223.253 255.255.255.255
An entry like this would allow any address starting with 66.12.223 to send e-mail:
66.12.223.1 255.255.255.0
Then end and restart your SMTP server.