A Separate Lane for Each Mailbox Provider

Take a campaign to 10,000 addresses: 6,000 on Mail.ru, 3,000 on Gmail and 1,000 on everything else. For you it is one campaign. For Estismail it is several separate streams, one for each provider. We call them lanes.

Why split it? Because providers don't compare notes. Gmail may have known your domain for years and trust it, while Yandex sees it for the first time. Mail.ru may be accepting emails happily while Outlook suddenly starts rejecting them. If a campaign went out as one stream, we would have to choose: either push at a speed that is risky for a cautious provider, or slow everyone down because of one. With lanes, there is no need to choose.

What this means in practice

Each lane has its own test batch at the start, its own speed based on your domain rating at that particular provider, and its own pauses. In our example, a test batch goes to Mail.ru and to Gmail right away. Mail.ru accepts calmly and ramps up to its speed. If Gmail starts answering with rejections at that moment, only the Gmail lane pauses, while Mail.ru and the rest carry on as before. After the pause Gmail gets a test batch again. How pauses work is explained in the article on pauses, retries and stopping.

Estismail also reads server answers by each provider's own rules: the same words in an answer mean different things at different providers.

Which lanes there are

Mail.ru, Gmail, Yandex, Outlook, Rambler, Yahoo, iCloud and UKR.net each have their own lane. An address goes into a lane by the domain after "@": mail.ru, bk.ru, list.ru and inbox.ru go in the Mail.ru lane. Which domains belong to which provider is recorded in the Estismail reference, and domain lists are in the articles on mailbox providers.

There are usually few emails to small providers, so they are gathered into two shared lanes. "German" covers GMX, Web.de, T-Online, Freenet, Mail.de, Online.de and Arcor. "Other" is everyone else, including company mail on their own servers. These groups also get a test batch and ramp-up, but they have no domain rating of their own, and their speed is the same as at a rating of 5. Emails in such a group go to hundreds of different servers, and a rejection from one of them does not mean the whole group is rejecting. So the test batch of a group fails only if 3 "spam" rejections arrive from 2 different domains.

The lane's speed is shared

A campaign is sent by several of our servers at once. A lane's speed, for example 300 emails per minute to Mail.ru, is 300 emails from all servers together, not from each one. How these servers share the work is explained in the article on sending servers and public servers.