Luggage Delivery on Magome to Tsumago Trail

Hoping for some clarification regarding luggage delivery service on the Magome to Tsumago Trail. Planning to visit the area in May and hike the trail on 20th May. However some website have indicated that the luggage delivery service is not available at that time and others are advising that the service is available all the time. If service is unavailable, any suggetions as to how to get luggage from Magome to Tsumago without lugging it on the trail would be greatly appreciated.

However some website have indicated that the luggage delivery service is not available at that time.

These websites are out-of-date. In 2015, the service will be offered daily between March 21 and November 30 as explained here:
http://www.japan-guide.com/e/e6078.html

and others are advising that the service is available all the time.

If they refer to the particular luggage-forwarding service, then they are wrong. A year-around service has never been offered. They may refer to the more general (next-day) delivery services that are described here:
http://www.japan-guide.com/e/e2278.html