If a domain has no MX record in the name server, but an email is sent to the domain, the mailserver trys to deliver the e-mails trough the IPv4 address in the A-record of the domain.
This is not always desired. To prevent this, there are records which are called "Null-MX Record". This tells the mail server that a delivery of emails is undesirable.
Of course, you have the ability to create such a record for your domain in our nameservers.
This can be done in your INWX customer area under the menu item "Name Server" as follows:
1. By clicking the "eye symbol" the DNS records of your domain are displayed
1. Click "Add Entry"
2. Leave the field "Name" blank
3. Select the type MX
4. In the field "Value" enter a point
5. In the "Prio" priority 0 must be entered
5. Finally, click "Save"
The Null-MX record is now configured as desired.
Further information is available at the following links: