The simple version: a customer asked us to. The Maysoft team had served HCL Domino email security customers for two decades. When the time came to step back, they reached out to DuoCircle with one condition: take care of these customers, and do not damage what we built.
That is the same condition under which DuoCircle was founded in 2014, when we acquired an email-hosting customer book on the same rule. Twelve years and over 50,000 organizations later, the rule still runs the company. SpamSentinel and InboxGenius are the products that came across in that handoff, and they are still maintained because the customers running them still need them maintained.
SpamSentinel sits inside DuoCircle's broader Protect portfolio, alongside Spam Filtering, Phishing Protection, and Visual Mail Verification. SpamSentinel is the Domino-native option in that lineup. The other three are for Microsoft 365 and Exchange shops.