sending error

Hi,

When I set the email to a local domain, the form with error of : There was an error trying to send your message. Please try again later.

When I set the Mail To an external email address, the form is working fine.

For example : Domain : https://test.abc.com
If the form send to [email protected], it got error.
If the form send to [email protected], it’s work.

Any idea what is wrong?

Thank you.

Regards,
Jess