HubSpot launched a free tool, drove stellar growth
June 1, 2019•47 words
"So, working on those rough numbers, the email signature generator has generated approximately $64 million in net-new customer revenue for HubSpot since it's inception."
Source: The world's most effective B2B marketing campaign (via G2.com)
...dunno if that really counts as a campaign, but hey, splitting hairs.