How to fix this: if your real error is:
SQLSTATE[08S01]: Communication link failure: 1153 Got a packet bigger than 'max_allowed_packet' bytes

You can not edit the servers my.cnf file from inside WHM, you will need to edit this file using she ssh command line. To learn how to connect to your server using ssh please see:

http://docs.cpanel.net/twiki/bin/view/AllDocumentation/CpanelDocs/ShellAccess

Once you are connected to your server with the root login using ssh, you will want to issue the following command to edit my.cnf:

# nano -w /etc/my.cnf

In this file you will want to add a line under the [mysqld] section with the following contents:

max_allowed_packet=16M

You will now want to press Ctrl + O to save, and then Ctrl + X to exit. You will now want to restart the MySQL server through WHM or on the command line with:

 # /etc/init.d/mysql restart

This will update the max_allowed_packet for cPanel/WHM's mysql.

If you still get the error increase 16M to 100M etc...

This will clear up the 500 error with mass mailing from OX Admin.

~W~