wbwp on "[Plugin: Contact Form 7 Vers. 3.4.2] how to alter wpcf7-list-item-label"

Hello,
I use the radio button feature with contact-form-7 plugin to let the user select among different email addresses. When I look to the page I see something like

o name1@email.com
o name2@email.com

Additional or instead of the email address I want to show the administrative function of someone like "President", "Treasurer" etc.

I tried already to alter the checkbox.php like

...
          foreach ( (array) $tag->values as $key => $value ) {
		$checked = false;

		if ( $is_posted && ! empty( $post ) ) {
			if ( $multiple && in_array( esc_sql( $value ), (array) $post ) )
				$checked = true;
			if ( ! $multiple && $post == esc_sql( $value ) )
				$checked = true;
		} else {
			if ( in_array( $key + 1, (array) $defaults ) )
				$checked = true;
		}

		if ( isset( $tag->labels[$key] ) )
			$label = $tag->labels[$key];
		else
			$label = $value;

		$item_atts = array(
			'type' => $tag->basetype,
			'name' => $tag->name . ( $multiple ? '[]' : '' ),
			'value' => $value,
			'checked' => $checked ? 'checked' : '',
			'tabindex' => $tabindex ? $tabindex : '' );

		$item_atts = wpcf7_format_atts( $item_atts );

		if ( $label_first ) { // put label first, input last
			$item = sprintf(
				'<span class="wpcf7-list-item-label">%1$s</span>&nbsp;<input %2$s />',
				esc_html( $label ), $item_atts );
		} else {
			$item = sprintf(
				'<input %2$s />&nbsp;<span class="wpcf7-list-item-label">%1$s</span>',
				esc_html( $label ), $item_atts );
		}
/* This is what I added
if ($key == 0) $wb = " (President)";
if ($key == 1) $wb = " (Treasure)";
if ($key == 2) $wb = " (Member)";*/

		if ( $use_label_element )
                          $item = '<label>' . $item  . '</label>';
/* I chnged here by adding the $wb */
		$item = '<span class="wpcf7-list-item">' . $item . $wb . '</span>';
        //$item = '<span class="wpcf7-list-item">' . $item . '</span>';
		$html .= $item;

		if ( false !== $tabindex )
			$tabindex += 1;
	}

This works fine and I get this result:
"Please select one of the following email addresses to sent your post
o xxx@xxx.org (President)
o yyy@yyy.org (Treasure)"

But when I submit the form I get this error:
"Failed to send your message. Please try later or contact the administrator by another method."

I guess it is because the php took the whole line "xxx@xxx.org (President)" as the email address and this causes the failure.
How can I achieve that only the mail address is taken from the line?

http://wordpress.org/plugins/contact-form-7/