Email form gives "Server error", no validation?

Hi everybody,
When I enter an Emailadress in the Emailform without the @-Sign and press submit i’m getting a "server error Sorry, something went terribly wrong! 0 - Address in mailbox given [emailadress] does not comply with RFC 2822, 3.6.2"
Can somebody please tell me how to prevent this.
In the system.yaml the
debug: false

display: false
log: true

and in for the form (onepage-website)

rule: email
required: true

why there is not just a validation note near the field of the form?
Thank you very much

i tried it as well with the demoskeleton,
same Server error.
Isnt there another way to handle this failure?

Check your for the following markup:

- name: email
          label: Email
          placeholder: Enter your email address
          type: text
            rule: email
            required: true

type:texthas to be type:email

Thanks very much sebbb!!
that solved the problem.