Validate email address is deliverable before creating account

[sentry-io]

From time to time, users will typo an email address (e.g. gmail.comm), but we'll create an account and attempt to verify the email address anyway. Our mail service, Mailgun, will reject the address immediately and then AnyMail, the mail library raises an exception.

We should validate that the email address is deliverable before creating the account and return an error to the user if it isn't.

I know Mailgun has a REST API for validating email servers. Does AnyMail have an API that can use it? I don't want to add a Mailgun dependence if possible.

Sentry Issue: BOOTCAMPS-17Q

AnymailRequestsAPIError: Sending a message to [email protected] from MIT Bootcamps <[email protected]
Mailgun API response 400 (BAD REQUEST):
{
  "message": "'to' parameter is not a valid address. please check documentation"
}
(3 additional frame(s) were not displayed)
...
  File "anymail/backends/base.py", line 95, in send_messages
    sent = self._send(message)
  File "anymail/backends/base_requests.py", line 60, in _send
    return super(AnymailRequestsBackend, self)._send(message)
  File "anymail/backends/base.py", line 125, in _send
    response = self.post_to_esp(payload, message)
  File "anymail/backends/base_requests.py", line 82, in post_to_esp
    self.raise_for_status(response, payload, message)
  File "anymail/backends/base_requests.py", line 93, in raise_for_status
    raise AnymailRequestsAPIError(email_message=message, payload=payload, response=response,

Error sending email 'Verify your email' to ["[email protected]"]

[HamzaIbnFarooq]

AnyMail works just like a proxy in sending emails (to Mailgun in our case). It doesn't have any email validation mechanism and totally depends upon the Mailing service it's using underneath.

If we want to proceed with email validation then we have to add the Mailgun API dependency (https://www.mailgun.com/email-validation/email-validator/).

Do we have any Mailgun account with this API enabled?

[pdpinch]

We need to consider the cost implications for this API from Mailgun.