No MX, no mail.. The MX record of a DNS is telling other servers where the mail should go to..
You will need to creat a MX record in (your?) DNS server that is pointing to your mailserver.
If you run your own DNS server, all you will need to do is within ISPconfig go to DNS manager > the-domain > Records, and click on New under MX.
Enter in Host: @ and in Mailserver the 1st domain of your server**
** The one you set in Management > Server > Settings (the Domain)
Aftert this do the dnsreport test again, and see if it's any better.
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