CoreSource, now Trustmark Health Benefits | 3,140 followers on LinkedIn. About CoreSource, now Trustmark Health Benefits: Trustmark Health Benefits, Inc. is a leading national health benefit plan administrator with 44 years of industry experience. We are part of the Trustmark family of companies, one of the leaders in benefits for over 100 years. Trustmark Health Benefits serves the needs of over one million members nationwide each year, handling claims of over $2.5 billion in 2018 alone.