ERROR: Misconfigured "Email To" address.

The contact form has stopped sending an email with an enquiry to a email address linked to the main domain name of the site. All other emails, not of the main domain, continue to receive a copy of the completed form.

When I remove all other addresses and just leave the callback email address in the email to: box the following error appears: ERROR: Misconfigured “Email To” address.

This email address is correct and if you send from another email to that address it is received. Also the system sends a confirmation email correctly when the form is filled. It just does not send an email to any email that is linked to the main domain the website is on.

I have tried switching off different plugins and it still happens. This problem began occurring yesterday – there had been no update or changes made to the site by me between receiving the last completed form at 10.35 and realising we were not getting any forms later that day.

Any thoughts on a fix for this?

Help very welcome

Nick