Hmmm let me wrote a technical post πŸ™‚

This morning a friend of mine called me cause he was experiencing some issues on his linux server, and q-mail. Mails queue was growing and strange errors started appearing into logs.
Issue identified: all mails to gmail accounts bounced with error “System resources temporarily unavailable. (#4.3.0) I’m not going to try again; this message has been in the queue too long.”

The issue was related to the module IPV6 not properly loaded (or not loaded at all) on the RHEL kernel (v 5.6, with parallels plesk 10.x).

Below the fix (hope useful for someone else and many thanks to Bono). It seems the first IPV6 issue I’ve encountered πŸ™‚

Step-by-step fix:

Enable IPV6 in RHEL:
Add the below entry in the modprobe.conf file
(use nano or vi, as you prefer)

# nano /etc/modprobe.conf

alias net-pf-10 ipv6
# alias ipv6 off
# options ipv6 disable=1

Change the β€œ NETWORKING_IPV6” parameter value to yes in the netwok file.

# nano /etc/sysconfig/network

type this command and add to the end of the file these two lines.
# nano /etc/sysconfig/network-scripts/ifcfg-eth0
IPV6INIT=yes # Enables IPv6 addressing on interface.
IPV6_AUTOCONF=yes # Enables EUI 64 auto-addressing.

After that, a machine reboot was needed. And then… EUREKA… inet6 address was set (and shown in ifconfig) and q-mail queue started decreasing.

Some useful hints:
to see the q-mail queue lenght via ssh:
# /var/qmail/bin/qmail-qstat
to force qmail to process the queue:
# kill -ALRM `ps ax | grep qmail-send | grep -v grep | awk '{print $1}'`

(we experiencing that the qmail queue could take a long time to purge the “blocked-in-queue” message, even if new message are sent immediately)

More info here: