Large self-directed custodian Mainstar Trust is a well-established self-directed retirement custodian with over 120,000 customers and $8.5 billion in custody assets, indicating a broad potential for upsell of custody-related services and higher-touch SDO offerings to scale with their existing client base.

Growth potential buyers With revenue in the $25M-$50M range and rapid growth history suggested by rebranding and large asset base, there may be opportunities to target Mainstar for enhanced technology integrations, white-glove support, and premium compliance tools as they scale.

Technology modernization Current tech stack includes marketing, security, and automation tools (LinkedIn Ads, Mailchimp, Mimecast, KnowBe4, reCAPTCHA, Google Search Console). This suggests openness to partnerships around security, customer experience automation, and regulatory/compliance tech enhancements.

Compliance and security focus Use of KnowBe4 and reCAPTCHA indicates emphasis on security awareness and bot protection; opportunities exist to offer advanced cybersecurity, risk management, and phishing-resistant solutions tailored to retirement plan custodians.

Competitive positioning As one of the largest national self-directed custodians with a sizable customer base, Mainstar is positioned to leverage scalable integrations and enterprise-grade solutions that differentiate from smaller peers and align with mid-market to enterprise retirement service providers.