Email send rate calculator
Enter how many messages you're sending and how fast you can send, to see how long the send takes. Add your own per-provider throttles to find the bottleneck.
Result
100,000 messagesExample: type your own numbers above.
- Your capacity
- 20,000 an hour (333.3 a minute, 5.56 a second)
- At full capacity
- 5 h
How it works
A send takes as long as its slowest part. That's either your own sending capacity (how many messages your servers or your email service can hand over an hour), or a mailbox provider that only accepts your mail at a certain rate.
Mailbox providers such as Gmail and Outlook.com limit how fast they accept mail from each sending IP address and domain. The limit depends on your reputation: how much mail you've sent before and how often people mark it as spam. When you go over it, the provider answers with a temporary error (a 4xx code), and your server tries again later. The page doesn't guess these limits. Enter the rates you see in your own logs.
A new IP address or domain has no reputation yet. Warm it up: start with small daily volumes to your most engaged readers, and increase them step by step over a few weeks while the bounce and complaint rates stay low.
The calculation assumes the rest of your list goes out while a throttled provider waits, which is how most mail servers queue. For the network side, the transfer time calculator shows how long data takes to move.