Brian Kolfage, the veteran behind the GoFundMe campaign that was raising money for a wall along the southern US border, reportedly grew a lucrative email list using shadowy techniques.

Kolfage has, in the past, operated websites that reportedly published false stories.

According to NBC News, Kolfage claims to have gathered 3.5 million email addresses thanks to the 'Build the Wall' campaign.

Brian Kolfage, the veteran who created the GoFundMe campaign to raise money for the wall, now has a potentially lucrative list of emails thanks to the fundraiser, according to NBC News.

NBC News reported that Kolfage, who was associated with websites that published false stories and had pages shut down by Facebook, claims to have gathered 3.5 million email addresses through his border wall campaign.

NBC News, which spoke to former employees and looked at public records, reported that Kolfage has repeatedly created GoFundMe campaigns and published inflammatory fake stories pushed from websites that are allegedly associated with him. Through those online avenues, he has harvested email addresses of people who may be willing to donate to conservative causes.

Read more: GoFundMe is refunding all donations made to the 'Fund the Wall' campaign

Those addresses, NBC News reported, have allegedly been used to encourage people to support Kolfage’s websites, to buy a coffee brand he owns, or to be stored for future use by conservative campaigns.

Lindsey Lowery, a former staff writer at the now-defunct conservative website FreedomDaily, shared a text message with NBC News in which Kolfage discussed his email harvesting plans.

In the texts, Kolfage told Lowery in September 2017 that "we can make our own [petition] through the website to steal/collect emails."

Kolfage, Lowery told NBC News, would create a petition or campaign related to an article she wrote on FreedomDaily, and then embed the email bait in that article.

"People would get worked up about the subject matter, so they’d want to go sign the petition to add their name to the cause," Lowery said. "Brian is referring to 'stealing' the emails, in this text, because the people didn’t sign up to get spammed with his news. It was simply to be part of the petition. I believe that’s how he got his email distribution built up."

Kolfage has repeatedly denied owning FreedomDaily, but former employees and contributors showed NBC News emails, documents, and checks that show his home address as FreedomDaily’s corporate business address.

Kolfage told NBC News that he simply managed the finances and administration for FreedomDaily. The operation's real owner, he said, lives outside the country.

Right Wing News, a site he told NBC News he is part of, features a chief operating officer on its website named "Steven Smith." Smith's photo on the website, NBC News found, is a stock image. In October of 2018, Facebook removed pages like Right Wing News for "inauthentic behavior," according to the Guardian.

Political email lists can be extremely valuable. Once a campaign is over, Roll Call reported, the email list doesn't go away: It can be used to share other information (info from a super PAC or organization), or it can be rented or sold to other organizations and campaigns. In 2009, Politico even put together a list of the most valuable political email lists.

"There’s a reason the FEC considers these kinds of lists to have value," Emily Cain, a Democrat who lost race against Maine Rep. Bruce Poliquin, told Roll Call in 2016. She used her list to direct her supporters attention to a group that supported her in her campaign.