What is Manilla envelope?

The envelope slid across the table by Lorena’s secret source in Shenzhen, later brought out by Eleanor at the lodge in Malay, symbolizes Eleanor’s willingness to do anything to sabotage Nick and Rachel’s relationship. Between hiring a private investigator and following Nick to Malay to block him from proposing—both situations in which the manilla envelope is present—Eleanor increasingly shows that she is willing to stop at nothing to end her son’s relationship.