The problem is how to start a conversation.

We had a similar problem in the university. At the beginning of the semester, the students have to register for a Moodle server with additional material. So when they create an account, we have to send a few thousands of confirmation emails in a short period out of the blue, that makes Gmail/Yahoo/Outlook/Whatever unhappy.

The solution was to ask the students to send an email to the server half an hour before registering. It's not ideal, but it adds us to a secret list of known contacts of the student, so (most) emails are delivered.