Invalid settings in userdb: userdb returned 0 as uid

The setup is ISPConfig 3.1.6
lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 8.9 (jessie)
Release: 8.9
Codename: jessie

The server is in production mode for over one year and working great! some time ago I edited a mailbox and this problem happend. I corrected it and told myself bd problem. But it happend again this mornig and I did some test and it' salways there!

After editing any mailbox in the system. The following parameter are empty in `mail_user`table
uid = 0
gid = 0
maildir = empty filed ( nothing but not NULL)
homedir = empty filed ( nothing but not NULL)

And if the user tries to send and received from outlook it doesn't work!
In the log here is the error message: Invalid settings in userdb: userdb returned 0 as uid

Any idea?

 

That is it!
There is problems with what is in the filds in the mail tab!

I changed the values but I can't save the new values.
I get this error:
1- Uid-mapping cannot be changed if there are already mail users.

I gess I need to change the values in the ispdb!
The table for those values is dbispconfig.serveer.config
And Voila! it fix the problem

Thanks Till!