Akonadi won't start for Domain Users

Hi - first, the directory '/var/lib/mysql-files' exists, owned by 
root.root and has 755 permissions.

So it is not that.

Now - I am not sure if this is a bug or if I have done something wrong, 
but have been messing with the problem for a while now. I have a hunch - 
which may be way off, but ....

I'm running a CentOS based server, Nethserver, and have set up domain 
logins. I log into my Kubuntu desktop machines using a domain logon and 
get the user name '[email protected]@machine-name'.

Launching Kontact or Kmail fails to launch Akonadi. When I try to launch 
Akonadi, I get:

[email protected]@machine-name:~$ mysqld: [ERROR] Could not open 
required defaults file: /var/lib/nethserver/home/username/
mysqld: [ERROR] Fatal error in defaults handling. Program aborted!
org.kde.pim.akonadiserver: database server stopped unexpectedly
org.kde.pim.akonadiserver: Database process exited unexpectedly during 
initial connection!
org.kde.pim.akonadiserver: executable: "/usr/sbin/mysqld-akonadi"
org.kde.pim.akonadiserver: arguments: 
("--defaults-file=/var/lib/nethserver/home/username/.local/share/akonadi/mysql.conf", 
"--datadir=/var/lib/nethserver/home/username/.local/share/akonadi/db_data/", 
"--socket=/tmp/[email protected]/mysql.socket", 
"--pid-file=/tmp/[email protected]/mysql.pid")
org.kde.pim.akonadiserver: stdout: ""
org.kde.pim.akonadiserver: stderr: "mysqld: [ERROR] Could not open 
required defaults file: 
/var/lib/nethserver/home/username/.local/share/akonadi/mysql.conf\nmysqld: 
[ERROR] Fatal error in defaults handling. Program aborted!\n"
org.kde.pim.akonadiserver: exit code: 1
org.kde.pim.akonadiserver: process error: "Unknown error"
org.kde.pim.akonadiserver: Failed to remove runtime connection config file
org.kde.pim.akonadicontrol: Application 'akonadiserver' exited normally...

Permissions on /var/lib/username/ seem to be okay - it is the users home 
directory, and the users have no other (software related) problems. The 
user can also read the ~/.local/share/akonadi/mysql.conf file and access 
the ~./local/share/akonadi/db_data/ directory.

Listing the ~/.local/share/akonadi/ directory gives:

$ ll ~/.local/share/akonadi/
total 28
drwxr-xr-x  2 [email protected] domain [email protected] 4096 Apr 11 
10:36 ./
drwxr-xr-x 34 [email protected] domain [email protected] 4096 Apr 11 
09:53 ../
-rw-r--r--  1 [email protected] domain [email protected]  150 Apr 11 
10:36 akonadi_control.error
-rw-r--r--  1 [email protected] domain [email protected]  150 Apr 11 
10:36 akonadi_control.error.old
-rw-r--r--  1 [email protected] domain [email protected]    0 Apr 11 
10:36 akonadictl.error
-rw-r--r--  1 [email protected] domain [email protected]    0 Apr 11 
10:36 akonadictl.error.old
-rw-r--r--  1 [email protected] domain [email protected]  734 Apr 11 
10:36 akonadiserver.error
-rw-r--r--  1 [email protected] domain [email protected]  734 Apr 11 
10:36 akonadiserver.error.old
-rw-r--r--  1 [email protected] domain [email protected] 3660 Apr  3 
09:30 mysql.conf
lrwxrwxrwx  1 [email protected] domain [email protected]   40 Apr 11 
10:02 socket-Aspire-S3-391 -> '/tmp/[email protected]'/

If I have a look in /tmp, I see:

$ ll /tmp/
total 88
drwxrwxrwt 16 root                 root 4096 Apr 11 10:53  ./
drwxr-xr-x 24 root                 root 4096 Apr  3 12:22  ../
drwx------  2 [email protected] domain [email protected]  4096 Apr 11 
10:02 '[email protected]'/

For local users, Akonadi/ Kontact works, and listing 
~.local/share/akonadi/ gives

$ ll ~/.local/share/akonadi/
total 28
drwxrwxr-x  4 username usergroup 4096 Apr  3 09:29 ./
drwxr-xr-x 21 username usergroup 4096 Apr  3 09:29 ../
-rw-rw-r--  1 username usergroup  827 Apr  3 09:30 akonadi_control.error
-rw-rw-r--  1 username usergroup    0 Apr  3 09:29 akonadictl.error
-rw-rw-r--  1 username usergroup    0 Apr  3 09:29 akonadictl.error.old
-rw-rw-r--  1 username usergroup  230 Apr  3 09:29 akonadiserver.error
drwxr-x---  6 username usergroup 4096 Apr  3 09:30 db_data/
-rw-rw-r--  1 username usergroup 3660 Apr  3 09:28 mysql.conf
drwxrwxr-x  8 username usergroup 4096 Apr  3 09:29 search_db/
lrwxrwxrwx  1 username usergroup   23 Apr  3 09:28 socket-Aspire-S3-391 
-> /tmp/akonadi-username.RoDq2s

So I am thinking it is something to do with the @ in the domain user 
name, which is resulting in the inverted commas around the 
/tmp/'[email protected]' directory?

Anyway - I'm using the nextcloud mail client and Thunderbird for my mail 
now, but would like to go with the Kontact PIM if possible. Any help 
would be appreciated.

Cheers

Don