There were many similarities between CP/M and MS-DOS. Inspired by the 8-bit CP/M, Paterson’s 16-bit operating system used similar commands and some of the same programming interfaces, but it was a different internal implementation and used different file storage formats.
At Digital Research, Gary Kildall’s opinion was that MS-DOS infringed on their copyrights for CP/M. He was furious, and confronted both Bill Gates at Microsoft and IBM, but his lawyer recommended against a lawsuit. ”Rather than sue, Kildall agreed to license CP/M to Big Blue. But he was astounded that when the PC was released, IBM charged $240 per copy for CP/M, and only $40 for DOS.”  Needless to say, the Microsoft offering became the dominant operating system for the IBM PC.
Paterson denied any wrongdoing. “I told him [Kildall] I didn’t copy anything. I just took his printed documentation and did something that did the same thing.” 
Thirty years later, Bob Zeidman, a programmer and expert in software intellectual property cases, conducted a detailed forensic examination of the code of QDOS, CP/M and PC-DOS. His conclusion? “QDOS was absolutely not copied from CP/M, and MS-DOS showed no signs of copying either. Kildall’s accusations about Bill Gates were totally groundless.” 
To fix this:
Disable the webmail service in 'Module Status'
sudo nano /etc/mysql/conf.d/zentyal.cnf
and change this line as shown: innodb=on
then: service mysql restart
get the MySQL pass: sudo cat /var/lib/zentyal/conf/zentyal-mysql.passwd
then: sudo mysql -p
Execute this query: DROP DATABASE roundcube;
Run this script: sudo /usr/share/zentyal-webmail/enable-module
Re-enable the webmail service in 'Module Status'
Easy huh. Everything is working now. Think about it when you click Next.
#innodb = off
service mysql restart
is not enough. I must replace password for roundcube user at mysql too.
Zentyal generate password at this file /etc/roundcube/debian-db.php
and Mysql admin at this file /var/lib/zentyal/conf/zentyal-mysql.passwd.
mysql> use mysql;
mysql> update user set Password = PASSWORD('Password roundcube from debian-db.php') where User = 'roundcube';