ansible - example of using mail module to send one email for all hosts

mail_body.j2

# templates/mail_body.j2
{% for host in play_hosts %}
The {{ host }} says {{ hostvars[host]['result']['stdout'] }}
{% endfor %}

play.yml

---
- hosts: all
  gather_facts: False
  connection: local
  tasks:
    - shell: echo "hello"
      register: result
      
    - mail:
        host: example.com
        port: 25
        to: test@example.com
        subject: Test
        body: "{{ lookup('template', 'templates/mail_body.j2') }}"
      delegate_to: localhost
      run_once: True