Verify Email domain before sending report

[gogasca]

Validate email and domain before sending report.
If email/domain is not valid, write file to local disk.

[2019-11-25 21:52:57,282: DEBUG/Worker-8] Starting new HTTPS connection (1): api.mailgun.net:443
[2019-11-25 21:52:57,714: DEBUG/Worker-8] https://api.mailgun.net:443 "POST /v3/sandbox15e24507b5f94692b44644fc5424a152.mailgun.or/messages HTTP/1.1" 404 87
[2019-11-25 21:52:57,725: WARNING/Worker-8] {
  "message": "Domain not found: sandbox15e24507b5f94692b44644fc5424a152.mailgun.or"
}
[2019-11-25 21:52:57,726: WARNING/Worker-8] 404
[2019-11-25 21:52:57,727: WARNING/Worker-8] NOT FOUND
[2019-11-25 21:52:57,727: WARNING/Worker-8] Email failed! Something went wrong...:(