THERE WAS AN ERROR TRYING TO SEND YOUR MESSAGE. PLEASE TRY AGAIN LATER.

I am having a terrible time with my contact form! I keep getting the following error in a yellow border:

https://ashanti.co.za/accommodation/rates/special-package-rates/ – (its at the bottom of the page)

I have checked everything a million times and cannot see what is causing the problem.
I have checked with the hosting company to see if the email address is blacklisted, but it is not.

TO: an email address with the domain
FROM: [name] [surname] <email address with the domain>
ADDITIONAL HEADERS: Reply-To: [your-email]
Cc: my email address
MESSAGE BODY:
From: [first-name] [surname]
Email: [your-email]
Telephone: [telephone]
Nationality: [country]
Arrival Date: [date-start]
Accommodation Type: [accommodation]
Package: [package]

Message Body:
[your-message]