Last week, U.S. Attorney General Jeff Sessions held a joint-press conference with law enforcement officials from around the world to trumpet work by the FBI and other agencies that successfully brought down AlphaBay, the latest drug marketplace on the “dark web,” the anonymous, highly protected internet where big-money drug sales are conducted using cryptocurrency like bitctcoin. And on Monday, sentencing was announced in an individual case illustrating exactly how drug deals go down on the dark web. A few old-school mistakes led to two arrests, though.

Abudullah Almashwali, 31, a Yemeni national formerly residing in Brooklyn, was sentenced to 6.5 years in federal prison, announced U.S. Attorney Phillip A. Talbert, for selling cocaine and heroin.

Almashwali and Chaudhry Ahmad Farooq, 24, a Pakistani national also living in Brooklyn, went by the names “Area51 and “DarkApollo” on AlphaBay, and would mail out drugs from post offices in New York to people all over the United States and received payment in bitcoin. They were busted in May 2016 when undercover cops bought heroin from a dealear named “Area 51,” who mailed it to California.

Here’s how they were caught: Investigators used postal records to show that both bought postage that was used to mail the drugs, and damingly, investigators also connected an email address used by “Area51” and “DarkApollo” to Twitter, Instagram, and Facebook profiles used by Farooq.

Social media companies like Twitter and Facebook (which owns Instagram) regularly comply with law enforcement requests in cases like this.

While Almashwali was sentenced to 6.5 years in prison on Monday, Farooq, who pleaded guilty in February to conspiring to traffic heroin, isn’t scheduled to be sentenced until January 22, 2018. He faces a maximum sentence of 20 years.

Since AlphaBay was taken down last week, there’s been a freak-out on the dark web about who will get caught next. Interestingly, all it took was a ridiculously unsecured email for the drug marketplace to unravel.

The dark web is just like the regular internet, but in order to get online, a user must use a Tor browser which guarantees anonymity — as long as you don’t use the same email for the dark web and Instagram.