Lookup email in Sendgrid's drop/unsubscribe/block list

[jace]

When a user's email bounces, Sendgrid adds it to a block list and drops all subsequent email to them. This can be frustrating for users with new email accounts who keep trying and don't receive any email.

Hasjob's email validator (or the confirm page) should consult Sendgrid's API and give the user a heads-up if there's an issue, asking the user to contact support if necessary.

[pranshu-07]

@jace This is primary business logic of email service provider. They do in order to maintain their/client's IP reputation at ESP side.

I suggest you to:

1. Create a webhook at sendgrid platform on every blocked contacts (Blocked by sendgrid after getting bounced.)
2. Make a entry to your database.
3. If a user tries to register on your website, unblock them using API.
4. Unblock them using API (If available) else contact their support for it.

[jace]

Related: #226