Add Input Field in Simple Model Contact Form (smcf) plugin [closed]

It just wasn’t concatenated correctly (i.e. misuse of single/double quotes). This’ll work:

$output .= '<div class="colmsg"><label for="smcf-message">*' . __("Message", "smcf") . ': </label>
        <select name="">
  <option>Post1</option>
  <option>Post2</option>
  <option>Post1</option></select></div><br/>';