Unable to send email to some domains using IPv6 in InterScan Messaging Security Virtual Appliance (IMSVA)

Interscan Messaging Security Virtual Appliance 9.0 , Interscan Messaging Security Virtual Appliance 8.5

Last updated: 2025/05/08

Solution ID: KA-0003000

Category: Configure , Troubleshoot

Know what to do when you are unable to send email to some domains and the message tracking logs shows an error similar to this:

Connect to ipmailmx.internode.on.net[2001:44b8:8060:ff02:300:2:6:6]:25: Network is unreachable

However, if you ping the destination message transfer agent (MTA), an IPv4 address is returned.

This issue happens when the network environment is not fully IPv6 compliant.

You can resolve the issue by configuring the IMSVA MTA, Postfix, to use an IPv4 address only when sending emails. Do the following:

Login to the IMSVA shell.
Edit the main.cf file located under the /opt/trend/imss/postfix/etc/postfix directory.
Look for the line "inet_protocols" and set it to "inet_protocols = ipv4".
Save the main.cf file.
Restart Postfix using the command "service postfix restart".

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