Problem with sending out mail with www-data

[tomppa]

Hi,

We have a problem with sending out mails with a php -script for mailadressess with user@samedomain.com as www.samedomain.com.
The customer is using a different mailsolution than ISPConfig.

During the creation of the site the Local/External Mailserver was set to
Local Mailserver in ISP Site/Options and we changed it afterwards, but no
change.

Looking at /var/log/mail.log confirms that the relay is local and ISPConfig / Postfix is not doing a MX check for this domain.

What can we do to fix this ?

We are running IspConfig 2.2.19 and thank You for a great hosting platform.

BR, Tom