On their website, the hacker group Handala Hack Team said Patel "will now find his name among the list of successfully hacked victims".
The hackers published a series of personal photographs of Patel smoking cigars, riding in an antique convertible and making a face while taking a picture of himself in the mirror with a large bottle of rum.
Many of the records appeared to relate to his personal travels and business from more than 10 years ago
A US Justice Department official confirmed that Patel's email had been breached and said the material published online appeared authentic.
The FBI did not respond to a request for comment.
The hackers did not respond to messages.
Handala, which presents itself as a group of pro-Palestinian vigilante hackers, is considered by some researchers to be one of several personas used by Iranian government cyberintelligence units.
Handala recently claimed the hack of Michigan-based medical devices and services provider Stryker on March 11, saying they had deleted a massive trove of company data.
Alongside the photographs of Patel, the hackers published a sample of more than 300 emails, which appear to show a mix of personal and work correspondence dating between 2010 and 2019.
Reuters was not able to independently authenticate the Patel messages but the personal Gmail address that Handala claims to have broken into matches the address linked to Patel in previous data breaches preserved by the dark web intelligence firm District 4 Labs.
Alphabet-owned Google, which runs Gmail, did not immediately respond to a request for comment.
Iran-linked hackers - who initially kept a low profile after the United States and Israel launched co-ordinated strikes against the Islamic Republic last month - have increasingly boasted of their cyber operations as the conflict drags on.
In addition to the hack against Stryker, Handala on Thursday claimed to have published the personal data of dozens of defence company Lockheed Martin employees stationed in the Middle East.
In a statement, Lockheed Martin said it was aware of the reports and had policies and procedures in place "to mitigate cyber threats to our business".
Gil Messing, chief of staff at Israeli cybersecurity company Check Point, said the hack-and-leak operation against Patel was part of Iran's strategy to embarrass US officials and "make them feel vulnerable".
In 2015, teenage hackers broke into then-CIA director John Brennan's personal AOL account and leaked data about US intelligence officials.
with AP
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