class Notifier < ActionMailer::Base default :from => 'noreply@company.com' def instructions(user) @user = user # normal syntax xlsx = render_to_string handlers: [:axlsx], template: 'users/send_instructions', layout: false attachments["user_#{user.id}.xlsx"] = {mime_type: Mime::XLSX, content: xlsx} mail :to => user.email, :subject => 'Instructions' end end