Contact form problem - won’t work

I am using a Rapid Weaver site as second site after having been hacked on a Wordpress-site. Today I looked at the RW-site and found that sending a message via the standard Contact Form does result in a warning: I’m sorry, there seems to have been an error trying to send your email. Please try again.

My knowledge of Rapid Weaver is limited so I did not find a solution myself. What should I have to look to or do to solve this problem?

Cheers
Rudolph Smits