The website was shut down in 2013 by the FBI.
The NCA said in a statement that London residents Basil Assaf, Elliot Hyams, Jaikishen Patel, all 26, and James Roden, 25, were studying at Manchester University when they began trading drugs.
Another man, Joshua Morgan, 28, of Manchester, was involved in packaging drugs for the group.
James Roden, Basil Assaf and Joshua Morgan, three of the five men sentenced in the UK on Wednesday.
The five made 6205 individual sales of ecstasy, a total of 17kg equivalent to 240,000 tablets, through the post.
They netted about US$1.14 million but also received payments in cash or cryptocurrencies, the statement said.
The five were given the following terms on Wednesday by the Manchester Crown Court: Assaf: 15 years and three months; Roden: 12 years; Patel: 11 years and two months; Hyams: 11 years three months; and Morgan: 7 years and two months.
NCA senior operations manager Ian Glover commented: “These five men were interested only in making money. They had no regard whatsoever for the harm these drugs could do to their users.
“The FBI’s excellent work shut the site down in 2013 in a globally significant operation and information they shared with us enabled us to identify, arrest and successfully build this case.
“Sites on the dark net represent a new variation on old crimes and are dealt with accordingly.
“The NCA has the capability and determination to bring offenders targeting the UK to justice regardless of how secure they feel hiding behind technology."
Photo: courtesy NCA