If it only took one email for Donald Trump to raise more than $3.3 million, just think of the possibilities for the future of his campaign.

Of course, the operative word here is "if"—as in, if Team Trump's boast about raising so much, so quickly were true. It’s probably not.

Donald Trump’s fundraising operation has been riddled with rookie errors—it’s been unsophisticated, untested and very small throughout his presidential bid, leading digital marketing experts to question whether it would be possible to actually raise the extraordinary figures he claims to have raised in a single fundraising email he sent last week.

“Throughout the entire election process, Trump has had the weakest effort in terms of sheer list size, the frequency of sending and the number of unique subject lines, which is an indicator of… sophistication. He really is vastly outgunned by political opponents on the Republican and Democratic sides,” said Jordan Cohen, the Chief Marketing Officer at Fluent, an advertising technology company that works with campaigns on both sides of the aisle.

The presumptive Republican nominee’s campaign was in free-fall last week when their financial disclosures showed they had just $1.3 million on hand at the beginning of the month, compared to Hillary Clinton’s $42 million.

Trump’s aides scrambled to right the ship, arguing within two days of the public disclosures that the businessman had received a miraculous infusion of donations to his campaign.

“We just started our online campaign. Online mailing [Tuesday] did over $3 million. Donald, in an unprecedented move, agreed to match the first $2 million personally that came in. So we did over $5 million online yesterday, and we’re just starting the effort,” national finance chairman Steve Mnuchin said in an interview with the Fox Business Network.

Meanwhile, Trump spokesperson Hope Hicks told marketing industry publication Advertising Age that the Trump campaign raised “$3.3 million on Tuesday and $3.4 million” on Thursday.

If those figures sound fantastical, it’s because they’re likely to be bogus.

Using a very sophisticated digital marketing operation, the 2012 Obama campaign’s most successful appeal for donations, with the subject line “I will be outspent,” brought in $2.5 million.

And of course, who can forget when Trump misled the public about raising millions of dollars for veterans charities—forking over the cash only when called out through numerous media investigations.

Now digital marketing experts are viewing Trump’s current claims with deep skepticism.

“It’s just not plausible for Trump to have raised what he claims online from one email,” said Julia Rosen, the Director of Marketing at ActBlue, a progressive firm. “The Trump campaign has failed to do the basic digital organizing work, like collecting email addresses at every available opportunity. That’s meant he has an exponentially smaller list, and because he hasn’t been running a modern engagement program with the few people that are on the list, it’s likely the average list member is not very responsive to the rare asks Trump makes of them.”

Neither Trump’s digital director, Brad Parscale, nor its spokesperson, Hope Hicks, returned requests for comment.

Return Path, which evaluates digital campaigns by studying 2.5 million email users who have given them permission to view their email habits, took an in-depth look at the Trump campaign’s online fundraising efforts. Its data, first reported on by Advertising Age and also shared with The Daily Beast, sheds light on how unlikely it is that Trump was able to raise the money he claims to have.

Trump’s campaign made an elementary mistake in its first digital solicitation for donations last Tuesday: it used a new domain, www.donaldjtrump.com, rather than www.donaldtrump.com. Spam filters determine what is junk mail and what isn’t in part by looking at whether an email domain has sent emails before.

Because Trump’s email solicitation was sent from a new domain, a lot of spam filters caught the campaign.

From a digital marketing perspective, it was a disaster: due to spam filters, an incredible 60 percent of Trump’s appeals never even made it to individual inboxes, per Return Path’s data.

“Most of the emails were delivered to the spam folder, which is out of sight and out of view for his subscriber. Of those that reached the inbox, not a lot of people opened the email,” Thomas Sather, senior director of research at Return Path, told The Daily Beast. Sather added that an industry standard was for 10 percent or less of email appeals to be delivered to spam.

Of those emails that made it through to inboxes, just 12 percent were opened. Six percent of those emails were deleted without having been read, according Return Path’s data.

Trump also has a very small fundraising list: until last week, he had not sent out a single appeal for donations, largely the result of having funded his own primary campaign. But this means that his operation is seriously undeveloped.

“They have a very, very small list, especially when you compare that to other candidates, even those who have dropped out of the race,” Sather said.

Return Path’s data shows that Ted Cruz, who is no longer even in the presidential race, had a donor list that was 3.7 times larger in May than Trump’s donor list is today. And when you compare Hillary Clinton’s approximate donor list size with Trump’s, you find that Clinton’s list is seven times larger (Return Path measures the relative size of donor lists, but does not estimate overall donor list size).

In addition to this, marketing firm eDataSource estimated at the beginning of June that Trump’s list size was 1.1 million, compared to 9.4 million for Clinton and 5.3 million for Bernie Sanders.

Trump’s digital effort is also relatively unsophisticated compared to campaigns launched by Obama’s campaign in the past, which is considered a gold standard for political digital marketing. The Obama campaign used complicated A/B testing methods, writing up various donor appeals and shooting them out to small subsegments of their donor lists. The most successful marketing emails were then blasted out to the whole list.

Obama’s fundraisers also used segmentation: different marked groups would receive different donor appeals. For example, an individual who has previously donated would get a different email from an individual who has never donated.

Return Path’s data indicates that the Trump campaign made no efforts at segmentation or A/B testing.

“Could Trump have raised money through other digital efforts? It’s possible but it would be much more expensive. He could have raised money through social advertisements or Google AdWords [program],” Sather said, but the net donations would be far less because this is very expensive to do. This would also be rather unorthodox: the Obama campaign did the vast majority of their fundraising through email, which keeps costs down.

Taryn Rosenkranz, the founder of progressive digital marketing firm New Blue Interactive, said it was possible that the Trump campaign had expanded its list by using the Republican National Committee’s donors.

But Sather told The Daily Beast that Return Path’s data “conclusively” showed that Trump had not used the RNC’s list.

“I just don’t see how you could [raise these amounts of money] with a list that hasn’t been cultivated,” Rosenkranz said. “From the existing email list he has, there’s very little chance that he could raise that money from that email list.”

However, Donald Trump is getting an enormous amount of exposure, even though he is not paying for it.

In the 10 day period from June 10 to June 19, not a single Trump campaign advertisement appeared in the nation’s top 60 media markets. Despite this fact, surveys taken by the advertising technology company Fluent show that 48 percent of Americans believed they saw a Trump television ad over a similar timeframe.

The reason that Cohen thinks that the fundraising figures, however unlikely, may be possible is that “Donald Trump and his campaign have defied convention wisdom,” and his relatively small list is made up of “the most fiercely loyal, the most fanatically supportive.”

“I’m not in a position to say they’re lying. It is a huge number, but it is theoretically feasible,” Cohen said, however adding that on digital matters, “Trump has not really done anything, and has been on the record saying he doesn’t need to be data-driven.”

Other experts took a harder bottom line: Rosen said that Trump’s national finance chairman’s claim of $3.3 million in one day of fundraising through “online mailing” is just impossible.

“Trump’s email list is too small, not engaged properly and the campaign failed at some really basic practices when they sent the email,” she told The Daily Beast. “It’s yet another sign that Trump’s small unprofessional staff is hurting his ability to to run a modern political campaign.”

—with additional reporting by Alexa Corse.