Free tool · 100% in-browser
Sending throughput calculator
Work out how much you can send and how long a campaign takes: combine the per-vMTA message rate, the number of sending IPs, and a real-world efficiency factor to get throughput per hour and day, plus the estimated time to clear a given volume. Useful for PowerMTA capacity planning. Calculated in your browser.
Throughput FAQ
How is sending throughput calculated?+
Total throughput is the per-vMTA message rate multiplied by the number of vMTAs (sending IPs) sending in parallel, optionally scaled by an efficiency factor to model real-world throttling. From that, the time to send a given volume is simply the volume divided by the per-minute throughput.
Why use an efficiency factor below 100%?+
Because the theoretical maximum is rarely the real one. Mailbox providers throttle, defer, and limit concurrent connections, and your own retries and bounces eat capacity. A factor of 60–80% is a more realistic planning number than assuming every IP runs flat-out continuously.
Does this account for IP warm-up?+
No — it assumes IPs are already warmed and running at the rate you enter. During warm-up your real rate is far lower and ramps over time; use the IP warm-up scheduler for that phase, then this calculator for steady-state planning.
Where does the per-vMTA rate come from?+
In PowerMTA it maps to max-msg-rate on a domain or virtual-mta. Set it conservatively per provider and per IP reputation; pushing the number up doesn't help if the receiver throttles you. This tool just turns your chosen rate into throughput and timing.
Related: IP warm-up scheduler · deliverability calculator