This post has been updated.

Vicente Fox, the former president of Mexico, received a plaintive fundraising request this weekend. "You are our country's only hope," read the email, which urged him to make "a generous contribution."

The sender? Republican presidential nominee Donald Trump.

It was the second missive that Fox received to his personal email address this month seeking donations for the Trump campaign, according to a spokesman for the former president. On Sept. 9, Fox got a message from Trump that concluded, "I know you won't let me down friend."

This is puzzling for a number of reasons.

The first: Fox is no friend of Trump. In fact, he may be his most vocal foreign critic, having accused the real estate developer of being a "false prophet" and compared him to dictators. "Campaigning in Mexico?" Fox mocked Trump on Twitter after getting the first request for financial support. "Running out of money and friends?"

But secondly, and even more importantly: It is illegal for an American candidate to solicit funds from foreign nationals. The law was brought to the attention of the Trump campaign back in June, when reports surfaced that lawmakers in Scotland, England, Iceland, Australia and other countries were getting a barrage of fundraising emails from the Trump campaign. Two campaign finance watchdog groups, Democracy 21 and the Campaign Legal Center, filed complaints in June with the Federal Election Commission.

But the emails kept going out to foreign leaders. That prompted Democracy 21 and Campaign Legal Center to write a letter in July to the Justice Department, asking them to investigate whether the Trump campaign had "engaged in knowing and willful violations" of campaign finance laws, which could carry criminal penalties.

"They have been put on notice that they are illegally soliciting contributions from foreign sources," said Fred Wertheimer, president of Democracy 21. "This is one of the most arrogant acts I have ever seen in the world of campaign fundraising, where they are willing to completely ignore the statutes that prevent a federal candidate from soliciting contributions from foreign interests. It's pretty mind-boggling."

Trump campaign officials did not respond to queries about how Fox got on their email list. The missives were sent from email@goppresidential.com, a domain used by the Trump Make America Great Again Committee, a joint fundraising committee between Trump's campaign and the Republican National Committee. It is common for campaigns and committees to rent email lists in an effort to expand their donor pools, but Republican committee officials could not immediately provide information about where the committee obtained the list that it is using.

The domain goppresidential.com is registered to Dan Backer, a conservative election law attorney who wrote in an email that he was "not authorized to talk about this matter."

But Backer added that, "as a very general matter, speaking broadly about all email lists, you can go to any website and type in any email address you want. I imagine there probably is a certain kind of weirdo who would enjoy typing in random and/or seemingly ironic emails for kicks.  People are funny that way."

He also noted that "the mere presence of an email of a non-qualified contributor on a list does not equate to any intent to solicit a person, even a foreign individual," adding: "Intent matters."