https://www.worldagentdirect.com/del...ode=DLMSGR_ASC


"Travel agencies can refund a non-refundable ticket(s) when there has been a Delta schedule change if one or more of the following apply:

There is a cancellation of a scheduled flight and there is no Delta flight with a comparable routing available within 90 minutes of the original time of departure.
A change in the scheduled departure time of a Delta flight which exceeds 90 minutes.
A change in the routing of a scheduled Delta flight which adds one or more stops to the original itinerary.
A change in the routing of a scheduled flight which results in a scheduled arrival time of more than 90 minutes later than the originally scheduled arrival time."


The same policies apply if the ticket was purchased directly from DL.