openproject/app/views/user_mailer/_issue_details.text.erb

<%= "#{issue.tracker.name} ##{issue.id}: #{issue.subject}" %>
<%= issue_url(issue) %>

<%= t(:field_author)        %>: <%= issue.author        %>
<%= t(:field_status)        %>: <%= issue.status        %>
<%= t(:field_priority)      %>: <%= issue.priority      %>
<%= t(:field_assigned_to)   %>: <%= issue.assigned_to   %>
<%= t(:field_category)      %>: <%= issue.category      %>
<%= t(:field_fixed_version) %>: <%= issue.fixed_version %>

<% issue.custom_field_values.each do |value| %>
  <%= value.custom_field.name %>: <%= show_value(value) %>
<% end %>

<%= issue.description %>