"He is here using the cover of a tourist while conducting various meetings, taking pictures and gathering information", an Iranian counterintelligence official appears to have informed military prosecutor Hojatol-Islam Bahrami in March 2007, who then ordered Levinson's immediate arrest by "MOIS (Ministry of Intelligence) brothers" in a handwritten reply on the typed memo.
It wasn't immediately clear why the Trump administration told the family that Levinson nearly certainly had died as an Iranian hostage if the President himself wasn't convinced of it.
In their statement, the Levinson family condemned the Iranian regime, promising to continue to seek justice in their patriarch's death and to hold accountable "those in the USA government who for many years repeatedly left him behind".
Mr Levinson was working as a private investigator and was seeking information on alleged corruption involving former Iranian president Akbar Hashemi Rafsanjani and his family, sources familiar with his work said.
Some US investigators, at least until recently, believed Levinson was still alive, while officials at other US agencies believe he died perhaps years ago.
The email comes as Trump administration officials are calling on Iran to provide a more complete accounting of Levinson's abduction and his time in captivity.
Mr Levinson disappeared in Iran 13 years ago from the island of Kish off Iran's southern coast.
For years, US officials would say only that Levinson was working independently on a private investigation.
It mentioned on the time that the Central Intelligence Agency paid $2.5 million to Levinson's spouse Christine, accepting duty for his disappearance. The person said the information about Levinson had come from Iran's foreign minister. "That is the very definition of cruelty".
"We are going to spend the remainder of our lives ensuring of this, and the Iranian regime should know we is not going to be going away". We don't even know when, or even if, his body would be returned to us.
The family went on to thank the Trump administration and a number of members of Congress for their efforts to help locate and bring back Levinson to the United States. "He will never be forgotten - we will make sure of it".
But he also acknowledged that "it's not looking promising" and said Levinson, who had diabetes and high blood pressure at the time of his disappearance, had had "some rough problems".
"He was a great gentleman", he said.
The family received proof-of-life photos and a video in late 2010 and early 2011, but Levinson's whereabouts and fate were not known.
In November, Iran acknowledged for the first time in a filing with the United Nations that there was an "ongoing case" in the Public Prosecution and Revolutionary Court of Tehran for Levinson, despite having previously denied knowing about his whereabouts.
Levinson, who was Jewish, is survived by his wife, Christine, seven children, and numerous grandchildren.