Total Health Care began notifying 221,454 health plan members and physicians of a hacking incident on its employee email accounts.
A data breach notice said the email accounts had sensitive information about the company's members and physician partners.
A forensic investigation found that employee email accounts were accessed between Dec. 16 and Feb. 5 by an unauthorized third party.
Sensitive information that was in the email accounts includes Social Security numbers, birthdates, addresses and more.
The health plan said it has no evidence that any breached information has been misused, but it's offering free credit monitoring by CyberScout for those potentially affected for up to two years.
In response to the breach, Total Health Care has hired security experts to increase its security and has provided additional cybersecurity training to its employees.