The four mailbox providers

Every email lands with a mailbox provider, and each one decides for itself which senders to trust. So every address is sorted by the provider that receives its mail, and each provider is paced on its own.

Four buckets, one for each provider

The mail server decides

The bucket comes from who handles the mail, not from how the address looks. Take an address at a company. Its domain's mail servers are looked up, once for the whole domain. If that company's mail runs on Google, the address goes in the Google bucket.

Each bucket has its own quota

• Every sending domain has a quota with each provider.
• Mail drips into each bucket at its own pace, spread across the sending window.
• Each bucket grows only on its own day's evidence.

Traffic governance explains how a quota sets the pace, and when it grows.

Why four buckets

• Each provider judges for itself whether to trust a sender.
• So each bucket is paced on its own, and grows on its own record.
• Every provider sees your mail arrive at a natural pace: Natural pace, and why it isn't warm-up.