B737 MAX 8 flight crew reported inflight vibration caused by external power receptacle door left open by ground operations personnel.

Narrative

Aircraft climbed through constant light chop from 8;000 feet to FL250. As we were climbing out of FL250 to F 380; we heard and felt a vibration in the cockpit. All engine instruments looked normal. Upon further inspection; we suspected it was coming from the external power receptacle door. I did an in-flight phone patch with Dispatch through ZZZ OPS frequency and informed our Dispatcher of the situation. I wanted to discuss the situation with Dispatch because I didn't want to take an aircraft headed to ZZZ1 next to a non-maintenance base if the vibrations were not caused by the suspected external power receptacle door being left open. The Dispatcher said we should return to ZZZ if we thought that airworthiness was in doubt.The First Officer and I discussed the situation and we had no doubt about the airworthiness of the aircraft. We decided it was Safe and prudent to continue to our destination. The noise and vibration stayed constant throughout cruise and did not let up until we slowed down in the arrival and approach phase. Upon arrival at our destination; ZZZ2; the ground crew said the external power receptacle door was fully opened at 90 degrees when we arrived. Local ZZZ2 Maintenance was there to meet the aircraft and inspected the door. Logbook entry was made. Dispatch and ZZZ3 Maintenance Control were notified.This small mistake could have led to an inflight return. Maintenance Control told me that this error has happened many times already because the Ground to Cockpit communications panel is not in the same place as the ground power receptacle for the 737 Max. I hope Ground Ops gets more training on this difference and hazard.Pushback Crew forgetting to close external power receptacle door.