MXToolbox on a Mac
DNS, blacklist & email health lookups (cloud) · Email Deliverability & Reputation
MXToolbox is the go-to for email/DNS diagnostics — MX, SPF, DKIM, DMARC and PTR lookups, blacklist checks across 100+ DNSBLs, SMTP diagnostics and ongoing Delivery Center / monitoring with alerts. Free web lookups plus paid monitoring and a REST API (API key). Store the key in Keychain; great for one-off checks and continuous blacklist monitoring.
Run MXToolbox with FrontierStack
FrontierStack lists MXToolbox in its Email Deliverability & Reputation catalog. MXToolbox is a hosted service, so there is nothing to install — connect your account with an API token and FrontierStack watches it alongside everything you self-host: reachability, its published status, and alerts when it stops answering. Credentials stay in your Mac's Keychain.
Run it all from one Mac app.
FrontierStack installs, monitors and secures the whole stack — locally and across your fleet — from a single native macOS app.
Download FrontierStack