Why warmup matters
A new IP has no history. Sending a large volume on day one looks like abuse to many providers.
A gradual ramp lets providers observe consistent, wanted mail before volume peaks.
Start with your best recipients
Send first to the most engaged recipients, those who opened or clicked recently.
Keep list quality high during warmup. Remove bounced and unengaged addresses before you begin.
Increase in steps
Raise daily volume in steps and hold if bounces or complaints rise.
Split volume across the major providers rather than sending everything to one.
Day 1: [N] Day 2: [N] Day 3: [N] ...
Watch the signals
Track bounces, complaints, deferrals and blocklist status each day.
If a provider defers heavily, pause the increase and let it settle before continuing.