Strange error using phpMail from php form

OS type and version Ubuntu 20
Webmin version latest
![mailqueue 690x203](upload://9roFuv4OMjUZ7TxPmxqRpZiweKb.png)

I get a strange error trying to send a mail creted in a form and sent by using php mail. I have tested to php mail works by sending a testmail via ssh and it is no problem, but when I fill in the form the mails get stuck in the postfix mailqueue. See attached image.
The odd thin is the domain it try to connect to. This domain is what the VPS was called when created but that is all cleared out. Have I missed anything vital?
Also sending mails from USERMIN is no problem.
Please advise

Anders yuran |