When I send a direct email to support@mysite.com, Desk will create a new ticket as expected.

When I REPLY to an email sent from support@mysite.com, Desk will NOT generate a new ticket.

This is very bad.  How can I fix this?

In a separate system or application, I send a user an email with support@mysite.com as a LEGITIMATE reply/sender email.  I want them to be able to reply, which will (should) generate a NEW support ticket.  Subsequent replies will then be linked to the ticket.

I expect Zoho to generate a NEW ticket when I send ANYTHING to my zoho support email.  The only time it should not generate a new ticket is when replies are of course from an existing ticket with a ticket ID, at which point the content is appended to the existing ticket as expected.