E-mail message to client from contacform doesn't work

Hello,
I have a problem. I placed several contactforms on my website. When a prospect leaves his e-mailadres he should receive an automatic e-mail with a text like: Dear xxxxx, thank you suscribing to our social media plan. I filled this in the following area’s on the contactform.

Autoresponder from email address
Enter the from email address for the autoresponder. (Standaard: (Email address hidden if logged out) )
(Email address hidden if logged out)

Tekst Automatisch Antwoord
Vul een bericht in dat zal worden verstuurd naar het e-mail adres van de gebruiker zodra hij het formulier heeft verzonden.

Wanneer leeggelaten zal er geen automatisch bericht worden verstuurd.

Unfortunately this automatic e-mail is never send to the customer. I already assest the matter to my wordpress host. They say they cannot fix this and that i should take this matter to the theme builder.

I will put the link to the contactform down under so you can test this for yourself.

Help will be appreciated