The Calendar vs mail.tm
Same instrument, two spec sheets — measured, not claimed.
The Calendar vs mail.tm: common questions
Which is more reliable, The Calendar or mail.tm?
On our scheduled checks, mail.tm leads on measured uptime — The Calendar at —% versus mail.tm at —% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.
Do The Calendar and mail.tm need an API key?
Neither needs a paid key — The Calendar is callable with no signup, and mail.tm is callable with no signup. Both are quick to prototype with; rate limits still apply.
Can I call The Calendar and mail.tm from the browser?
Yes — both The Calendar and mail.tm send CORS headers over HTTPS, so front-end code can fetch either directly with no backend proxy. That makes them easy to swap in a client-side app while you compare responses.
Are The Calendar and mail.tm free for commercial use?
The Calendar has unclear commercial terms, and mail.tm has unclear commercial terms. We track service terms and the data license as separate fields — see the Commercial use and Data license rows above, and confirm both before shipping either in a paid product.