Spam filters in Gmail, Outlook and Yahoo may have cost the GOP about $117 million in donations, according to a study

A recent study quantifies the economic impact of the controversy that has pitted Republicans against major email providers. According to the research, revealed by the New York Post (NYP), Republican candidates reportedly failed to secure the equivalent of about $117 million in donations from first-time donors during two incidents in 2025 in which Gmail, Microsoft Outlook and Yahoo massively flagged fundraising emails containing links to WinRed as spam.

The study, conducted by Cameron Ellis of the University of Iowa and Lars Powell of the University of Alabama, is based on data from the Federal Election Commission (FEC) and on inbox placement tests conducted by the Republican consulting firm Targeted Victory.

The authors identify two instances in 2025 in which spam filtering coincided with a sharp drop in donations from first-time contributors via WinRed, the platform associated with the Republican Party. During the same period, no comparable decline was observed in emails containing links to ActBlue, the Democratic Party's equivalent platform.

What the study measured and what the results were

The researchers identified two specific episodes in which WinRed links were penalized by spam filters:

Overall, the authors estimate that 142,126 donations from new contributors were lost. They estimate that loss at $117 million using the cumulative value over eight months of a first-time WinRed donor, about $827, rather than the amount of the first contribution, which was about $461. Google disputes that figure and considers it a theoretical estimate, not actual revenue.

What the study says 

The study does not conclude that there was intentional political bias. The researchers cross-referenced detailed FEC donation records, to distinguish between first-time and repeat donors on WinRed and ActBlue, with paired tests of inbox placement (same text, different link). In this way, they estimated how many donations were lost relative to the baseline and assigned them a monetary value.

In the authors' words, "a limited placement decision, at the link level, by a small number of email providers resulted in a quantifiable and economically significant drop in political fundraising, and that mechanism was only observable because private evidence from paired experiments was leaked into public reports."

Powell, a co-author, emphasizes that major providers "are not transparent enough" about how their filters work and that "we cannot read their minds."

The source: The SURBL list

According to previous reports by the New York Post, Gmail used an external reputation list, SURBL, which flagged domains as suspicious. Targeted Victory detected that emails containing links to WinRed arrived with warnings stating "appears dangerous," while identical messages with links to ActBlue were delivered without issue.

Following pressure and coverage by the Post, Google confirmed in September 2025 that it had stopped using that signal. The authors note that, from that point on, the delivery of Republican emails returned to normal.

The study reignites Republican allegations of tech censorship. A GOP adviser quoted by the Post speaks of "overwhelming evidence" of a conservative disadvantage. In August 2026, Google announced a verified sender program for campaigns and PACs, designed to improve delivery. Bernadette Breslin of the NRSC presents this as an "opportunity to level the playing field" and accuses Google of using biased algorithms that marginalized Republican emails.

Google rejects the methodology and maintains that anti-spam protections are applied "equally, regardless of political affiliation."