I'm building something similar (Dead Simple Email - same category, different pricing structure). The moat criticism is fair and worth being honest about. The defensible part isn't the feature set, it's infrastructure and price. We run our own mail servers rather than reselling SES, which gives us direct control over deliverability and costs. That's what lets us charge $29/mo for 100 inboxes where AgentMail is at $200. Whether that's a real moat or just a head start is a legitimate question. Email deliverability is genuinely hard to get right at scale, but I can't say with confidence they won't eventually just absorb this. Building fast and staying cheap is the only real answer I have to that.