Preventing Third Party Relay Spam on Your iSeries AS400 SMTP Server

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.

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Last modified: November 7, 2011

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