MXToolbox integrations and automation

MXToolbox is where email administrators go when mail stops arriving: is the domain on a blacklist, does the SPF record still include the new sending service, did someone break the DMARC record during a DNS change? The MXToolbox API lets you run the same lookups from a workflow, so those checks happen every morning instead of after a customer complains. Lookups run on the same engine as the MXToolbox SuperTool and are addressed as api/v1/Lookup/{Command}/?argument=, for example an mx, spf, dmarc, dkim, smtp or blocklist lookup against a domain or IP address.

Each lookup returns its results grouped into Failed, Warnings, Passed and Timeouts lists, each entry with a name, an info text and a link, plus the command, argument, reporting name server and time to complete. That grouping is what makes automation useful: a brief can say “alert only if Failed is not empty” instead of asking anyone to read the raw output. A blocklist lookup checks an address against many lists in one call, and the Failed entries name the ones that matched, which tells you where to request delisting.

Requests carry the account’s API key, a plain UUID, in the Authorization header. A free account comes with a small starter allowance of DNS requests, each paid plan has a daily limit for simple and complex lookups, and the Usage method reports consumption. MXToolbox also applies variable rate limiting that answers with 403 errors, so retries should back off. A domain list of a few dozen entries checked daily is reasonable; checking every customer domain hourly is likely to exhaust the allowance.

MXToolbox also runs its own monitors, and the Monitor method returns the current status of the monitors you subscribe to; monitor queries need a paid API key. If you already have monitors, reading their status saves repeating lookups. DNS changes take time to propagate, and MXToolbox results can differ from what a specific resolver sees during that window, so a single failed check right after a change is a reason to recheck, not to page someone at night.