TYPO3 Core

When using this form configuration I get an warning (exception in development context).

prefix = tx_form
confirmation = 1
postProcessor {
    1 = mail
    1 {
        recipientEmail = info@domain.com
        senderEmail = info@domain.com
        subject = Contact form
    }
}
10 = TEXTLINE
10 {
    name = company
    label {
        value = Company
    }
}
20 = TEXTLINE
20 {
    name = name
    placeholder = Your name
    label {
        value = Name
    }
}
30 = TEXTLINE
30 {
    name = email
    placeholder = Your emailaddres
    label {
        value = Emailaddress
    }
}
40 = SELECT
40 {
    name = Inform me about
    label {
        value = Please send me some info
    }
    10 = OPTION
    10 {
        data = Webdesign
    }
    20 = OPTION
    20 {
        data = TYPO3
    }
    30 = OPTION
    30 {
        data = Something else
    }
}
50 = TEXTAREA
50 {
    cols = 40
    rows = 5
    name = message
    label {
        value = Message
    }
}
60 = SUBMIT
60 {
    class = btn
    name = 5
    value = Send
}
rules {
    1 = required
    1 {
        breakOnError = 0
        showMessage = 1
        message = Required
        error = This field is required
        element = name
    }
    2 = email
    2 {
        breakOnError = 0
        showMessage = 1
        message = (john.doe@domain.com)
        error = This is not a valid email address
        element = email
    }
}