I planed to upgrade zimbra from 8.0.4 to 8.0.6, when trying to run ./install.sh, I got following error:
Operations logged to /tmp/install.log.31959
Checking for existing installation...
ZCS upgrade from 8.0.4 to 8.0.6 will be performed.
ERROR: Unable to reach the Zimbra License Activation Server.
License Activation is required when upgrading to ZCS 7 or later.
The ZCS Network upgrade will automatically attempt to activate the
current license as long as the activation server can be contacted.
You can obtain a manual activation key and re-run the upgrade
by specifying the -a activation.xml option.
A manual license activation key can be obtained by either visiting
the Zimbra support portal or contacting Zimbra support or sales.
I tried to telnet to the license.zimbra.com
telnet: Unable to connect to remote host: Connection timed out