Jenelle Evans and David Eason were in the car when David opened their mail and discovered a disturbing letter ... adding major insult to injury for the couple.
According to the 911 call -- made by Jenelle -- her husband opened a letter addressed to her in her car when a powder came pouring out of it ... causing him to throw the rest of the mail outside on the ground.
Jenelle tells the operator the return address made it seem like it was from Brunswick County Clerk ... making it look like important mail. She says David -- obviously -- was freaked out by it.
As we reported ... Jenelle and David received the suspicious package on May 15, just moments after the couple lost custody of their 2-year-old daughter, Ensley.
Now we know Jenelle's the one who phoned 911 to report the substance when they got back from the hearing, and cops responded shortly after to file a report. It's still unclear if the powder was a real threat or a hoax.