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##### SUMMARY
mail module does not send email with Date header. It should send email with "Date" header automatically without any manual email header manipulation.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
mail

##### ANSIBLE VERSION
```
ansible 2.8.1
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/home/yclee/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/dist-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.15+ (default, Nov 27 2018, 23:36:35) [GCC 7.3.0]
```

##### CONFIGURATION
(None)

##### OS / ENVIRONMENT
Ubuntu 18.04

##### STEPS TO REPRODUCE
N/A

##### EXPECTED RESULTS
email should have Date headers

##### ACTUAL RESULTS
email did not  have Date headers and I have to manually insert it

port=dict(type='int', default=25),
            sender=dict(type='str', default='root', aliases=['from']),
            to=dict(type='list', default=['root'], aliases=['recipients']),
            cc=dict(type='list', default=[]),
            bcc=dict(type='list', default=[]),
            subject=dict(type='str', required=True, aliases=['msg']),
            body=dict(type='str'),
            attach=dict(type='list', default=[]),
            headers=dict(type='list', default=[]),
            charset=dict(type='str', default='utf-8'),
            subtype=dict(type='str', default='plain', choices=['html', 'plain']),
            secure=dict(type='str', default='try', choices=['always', 'never', 'starttls', 'try']),
            timeout=dict(type='int', default=20),
        ),
        required_together=[['password', 'username']],
    )
    username = module.params.get('username')
    password = module.params.get('password')
    host = module.params.get('host')
    port = module.params.get('port')
    sender = module.params.get('sender')
    recipients = module.params.get('to')
    copies = module.params.get('cc')
    blindcopies = module.params.get('bcc')
    subject = module.params.get('subject')
    body = module.params.get('body')
    attach_files = module.params.get('attach')
    headers = module.params.get('headers')
    charset = module.params.get('charset')
    subtype = module.params.get('subtype')