Domain Change in website

[Jose Gosalbez]

Hi.

I had a ISPConfig account with a domain called "domain.com" and I need to change the domain for "newdomain.com" in the ISPConfig panel.

The domain has more than 500 accounts.

After I have just removed the old domain entries in co-domain and added the new one entries for "newdomain.com"

I can login into webmail with my "user123@newdomain.com" and I can send messages correctly. But when I try send a email from a external account (gmail) to this user the Postfix returns the following error:

-----------------------------------------------------------------
This is the Postfix program at host linuxserver.mydomain.com

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The Postfix program

<user123@linuxserver.mydomain.com> (expanded from
<user100@webcolegial.com>): can't create user output file. Command
output: procmail: Couldn't create "/var/mail/user123" /bin/sh: let:
HD_QUOTA=*1024: syntax error: operand expected (error token is "*1024")
/bin/sh: line 1: [: !=: unary operator expected find: /var/mail: Permission
denied

----------------------------------------------------------------------

Why fails?

Can I change a domain name in a site that have users ?

Must I create a new site with the new domain and delete the old one?

thanks !