Summary: Fix the 'Sendmail: Gethostbyaddr ipv6 Failed' error on aix.
Date: Around 2013
Refactor: 6 January 2025: Checked links and formatting.

I got these errors in my syslog server after installing new AIX servers on (almost) the latest Technology Levels, for as well AIX 5.3 as for AIX 6.1:

message forwarded from aixbox: sendmail[475316]: gethostbyaddr(ipv6:::1) failed: 1

It turned out that since a few technology levels ago sendmail has become IPv6 aware and is now not able to resolve hosts over IPv6. It is solvable by editing these two files and adding the showed lines:

• /etc/hosts

::1 loopback localhost

• /etc/netsvc.conf

hosts=local,bind4

This solved the problem, no restart needed of anything. The messages just disappeared.

IBM Technote