[Bug] Cortex Mailer Responder does not add Date header (per RFC5322)

[AM-CERT]

Describe the bug
Cortex Mailer Responder does not add Date header (per RFC5322) in email causing Undeliverable mail, invalid header section from Amavis.

To Reproduce
Steps to reproduce the behavior:

1. Configure Mailer Responder
2. Send email using type case or case_task

Expected behavior
Email delivery to he recipient

Work environment

• Client OS: Linux
• Server OS: Linux / Docker
• Browse type and version: Chrome
• Cortex version: 3.1.7-1
• Cortex Analyzer/Responder name: Mailer
• Cortex Analyzer/Responder version: 1.0

Possible solutions
Add Date header before sending the email

from email.utils import formatdate

msg["Date"] = formatdate(localtime=True)

Thank you