redmine/app/views/messenger_settings/_messenger_text.html.erb

<p>
  <%= f.text_field mf, size: size, label: l("label_settings_#{mf}") %>
  <em class="info"><%= l(:label_messenger_project_text_field_info) %> (<%= l(:label_default) %>: <%= Messenger.default_textfield(@project, mf) %>)</em>
</p>