One email shows Christie's top appointee at the bridge agency, Bill Baroni, looping in Stepien on a letter of complaint on the fourth full day of the September lane closures.
"Thanks," Stepien replied after being forwarded the letter from Mark Sokolich, the mayor of Fort Lee, where traffic backed up for hours, stalling school buses and emergency vehicles.
In another exchange, Stepien sends a complimentary message after Baroni told a legislative panel that the lane closures were part of a traffic study, a story that has since been discredited.
"I know it's not a fun topic ... but you did great," Stepien wrote in late November, a few weeks after Christie easily won re-election.
Christie maintains he didn't know about the lane closing operation but the scandal has cast a shadow over his administration and raised questions about his chances if he runs for president in 2016.
Stepien's lawyer says his client has done nothing wrong.
"The documents released today ... thoroughly discredit the committee's desperate attempt to paint Mr. Stepien as a central figure in the lane closure controversy," said the lawyer, Kevin Marino.
Stepien and fired Christie aide Bridget Kelly want the subpoenas thrown out based on their constitutional right against self-incrimination. The U.S. attorney's office is conducting a parallel criminal investigation into the lane closings, along with accusations that the Christie administration threatened to withhold aid to a city badly flooded by Superstorm Sandy unless the mayor approved a redevelopment project favored by the governor. Both Stepien and Kelly say they have been visited by FBI agents, though neither has cooperated, their lawyers said.
Reid Schar, a lawyer for the panel, claims the existence of additional Stepien emails bolsters the subpoena's validity.
Other people and organizations close to the Republican governor have complied or are in the process of turning over documents.
The panel also claimed in the filing that the legislators do not have the authority to grant immunity to Stepien and Kelly in exchange for the documents, or to hold them in contempt for failing to comply with the subpoenas. A judge has asked both sides to explore the question of immunity before she issues a ruling, perhaps by the end of the month.
The emails released Monday start on Sept. 12, while the lanes were still closed, and include exchanges on Jan. 8, the day before Christie was forced to retract an earlier statement that his staff had no involvement in the lane closings.
Stepien, a valued political adviser who was said to be in line to run a possible Christie presidential campaign, ran both of Christie's gubernatorial races and worked in the administration as a deputy chief of staff, a job Kelly took over. He previously ran a campaign for Baroni, a former elected official.
In a Jan. 8 email, sent as the scandal was busting open, Christie spokesman Colin Reed noted that Kelly's Twitter timeline contained photos of Christie and other staffers at Kelly's 40th birthday party.
"Maybe too late, but she may want to shut down everything on social media," Reed suggested to Maria Comella, Christie's deputy chief of staff and a member of his Cabinet.