Contact form working but customers getting an error

[king888]

I am on PS 1.5.3.1

Customers alway get error like this when they try to contact us via contact form page.

 

There are 1 error

1. an error occurred while sending message

 

 

But the email is actually sent to my address. So the email configuration is not an issue. Please help. This create bad customer experience.

 

 

Here is the link to my contact form page.

 

http://www.vitaminfa...troller=contact