Sending Speed: Test Batch and Ramp-Up
In this article
When you press "Send", a campaign to 100,000 addresses does not fly out in one second. First a small test batch goes to each mailbox provider, and only then does the speed start to grow. From the outside it looks like caution, and that is exactly what it is: in the first minute we learn how the provider treats this particular campaign, risking a couple of dozen emails rather than the whole list.
We do not limit the number of emails, though. Every email in the campaign will be sent, with no daily limits and no carrying the rest over "to tomorrow". Only the speed changes.
The first minute
The first 50 emails go to each provider. Then Estismail listens to what its servers answer: it waits at least 15 seconds until answers arrive for at least 80% of the emails, but no longer than a minute and a half. If the answers are clean, 50 more emails go out and are checked the same way. After the second clean test batch, the ramp-up begins.
But if the provider answers "spam" to any email of the test batch, or blocks the sender, or asks to slow down for half of the emails, sending to it pauses, while sending to the other providers goes on. What happens after that is explained in the article on pauses, retries and stopping.
Small providers are gathered into two groups, "German" and "Other", and their emails go to hundreds of different servers. One rejection there says nothing about the campaign as a whole, so a group's test batch fails only on 3 "spam" rejections from 2 different domains.
How the speed grows
After the test batch, every calm minute speeds sending up by one and a half times: 50, 75, 113, 170, 255 emails per minute and beyond. If new rejections arrive during a minute, the speed does not grow until things calm down.
Where to start and how high to go is decided by your domain rating at this provider, that is, its history with you. A domain the provider has trusted for a long time has no reason to crawl. A new one is better off not rushing.
| Domain rating at the provider | Start after the test batch | Top speed |
|---|---|---|
| 7.5 and higher | 300 emails per minute | no limit: from 20,000 emails per minute sending runs at full speed |
| 4,5–7,4 | 100 emails per minute | 8,000 emails per minute |
| 2,5–4,4 | 50 emails per minute | 1,500 emails per minute |
| below 2.5 | 50 emails per minute | 600 emails per minute |
The rating is taken at the moment the campaign starts, and how it is calculated is explained on the page about domain rating. If there is no history yet, we start from the middle and look at your other domains at this provider: a new domain will not get more trust than the weakest of them. And if sending from this domain to the provider had to be stopped recently, the campaign starts carefully.
In numbers: a new domain has a rating of 5, but not higher than the lowest rating of your domains at this provider over the last 7 days. After a stop within the last 7 days, the rating at the start is no higher than 2. The "German" and "Other" groups have no rating of their own; their speed is the same as at a rating of 5.
One more detail: the speed is counted for the whole campaign at once. 300 emails per minute means 300 from all our servers together, not from each.
A new domain
A provider does not know a new domain, and it needs the first days to get used to it. So a new domain has its own speed ceiling, regardless of rating, and it rises with each day of campaigns. After a couple of weeks of regular sending the ceiling disappears, and only the rating sets the speed.
The ceiling is this: in the first 2 days of campaigns 200 emails per minute, from day 3 to day 5 it is 500, from day 6 to day 10 it is 1,000. A campaign day is a day when at least 500 emails went out to the provider. A domain stops being new when it has 10 such days and 14 days have passed since the first campaign.
Complaints
A provider notices "this is spam" complaints from recipients faster than anything, and so do we. If complaints about your emails became noticeably more frequent than usual, then for the next day campaigns to this provider go slower. After a day the speed comes back.
For a new domain the trigger is 5 or more complaints in a day, if that is at least 0.05% of what was sent: then for a day the ramp-up runs as at the lowest rating, up to 600 emails per minute. For a domain with a history it is 0.1% of complaints, if that is twice its usual level over 30 days: then for a day the top speed is one row of the table lower.
With every calm campaign the rating grows, and the speed grows with it.
Thank you!
Tell us what was unclear: support@estismail.com. We will reply and fix the article.