"On Sunday evening, the vendor confirmed that FanDuel customer names and email addresses were acquired by an unauthorized actor. No customer passwords, financial account information, or other personal information was acquired in this incident."
FanDuel also stressed that this was not a breach of their systems or FanDuel user accounts and that the hackers did not acquire "passwords, financial account information, or other personal information" during the breach.
https://www.bleepingcomputer.com/news/security/fanduels-warns-of-data-breach-after-customer-info-stolen-in-vendor-hack/
Perhaps MailChimp would lose this one customer because of the said breach on their system.
And most likely there will be more costumers coming forward and admitted that they are the victim/s of such incident.