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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

if not secure_state and (username and password):
        module.warn('Username and Password was sent without encryption')
    msg = MIMEMultipart(_charset=charset)
    msg['From'] = formataddr((sender_phrase, sender_addr))
    msg['Subject'] = Header(subject, charset)
    msg.preamble = "Multipart message"
    for header in headers:
        
        for hdr in [x.strip() for x in header.split('|')]:
            try:
                h_key, h_val = hdr.split('=')
                h_val = to_native(Header(h_val, charset))
                msg.add_header(h_key, h_val)
            except Exception:
                module.warn("Skipping header '%s', unable to parse" % hdr)
    if 'X-Mailer' not in msg:
        msg.add_header('X-Mailer', 'Ansible mail module')
    addr_list = []
    for addr in [x.strip() for x in blindcopies]:
        addr_list.append(parseaddr(addr)[1])    
    to_list = []
    for addr in [x.strip() for x in recipients]:
        to_list.append(formataddr(parseaddr(addr)))
        addr_list.append(parseaddr(addr)[1])    
    msg['To'] = ", ".join(to_list)
    cc_list = []
    for addr in [x.strip() for x in copies]:
        cc_list.append(formataddr(parseaddr(addr)))
        addr_list.append(parseaddr(addr)[1])    
    msg['Cc'] = ", ".join(cc_list)