This sounds very impressive if the campiagn is really raising this kind of money and it's coming from WaPo:
[Trump's] campaign said late today that the mogul's Tuesday fundraising email to supporters had already generated an astounding $3 million (plus an additional $2 million Trump himself had promised in matching funds.)
"Raising such a huge sum in a short amount of time — through an email list that had never before been tapped for contributions — would make Trump's pitch for donations one of the most successful in American politics, according to veteran fundraisers. Because not every email recipient responds to a solicitation, experts estimate that it would require a list of as many as 6 million supporters to raise a sum as large as 3 million dollars in such a short period," reported Matea Gold.
"Digital fundraising experts were skeptical that Trump has been able to curate and maintain such a big list. But if he did pull off $3 million in a day, Democrats should be worried, they added. At such a rate, Trump could pull in more than $20 million online by the end of the month."