A domain that has never sent mail is not trusted or untrusted, it is unknown. Receiving servers treat unknown senders cautiously, and the way you move out of that category is by sending mail that people engage with, in gradually increasing volume, consistently.

Before you send anything

Set up authentication before the warm-up starts. Receivers form their view of the domain from the warm-up traffic, and on a misauthenticated domain that traffic fails their checks.

  • SPF: a TXT record authorising your sending service. It has a 10 DNS lookup limit, and a record over that limit fails silently.
  • DKIM: the provider gives you a key to publish. To confirm it is actually signing, open a received message and look for the DKIM signature in its headers; the dashboard status alone does not show that.
  • DMARC: start at p=none with a reporting address so you can see what is happening, then move to quarantine and reject once the reports are clean.
  • Reverse DNS and a valid return path, if you run your own infrastructure.

The ramp

Volume roughly doubles every few days, and that doubling matters far more than the exact figures. A four week ramp:

Week 1:  50 -> 200 per day
Week 2:  500 -> 2,000 per day
Week 3:  5,000 -> 10,000 per day
Week 4:  20,000+ per day

Two rules matter more than the numbers. Send every day, because a domain that sends 2,000 on Monday and nothing until Friday looks like a burst, not a business. And never skip a rung because you are in a hurry.

Who you send to matters more than how many

This is the part people miss. During warm-up, send to your most engaged recipients first, and expand outward. Opens and replies are positive signals. Deletions without opening are neutral at best. Spam complaints are severely negative.

Order your ramp by engagement:

  1. People who opened or replied in the last 30 days.
  2. Last 90 days.
  3. Last 180 days.
  4. Everyone else, if at all.

Sending to a two year old list on day three of a warm-up will produce bounces and complaints at exactly the moment receivers are deciding who you are.

Watch the right numbers

Bounce rate under 2% and complaint rate under 0.1% are the working targets, not the published limits. The published limits are where enforcement begins, which is far too late to be your alarm.

Segment by receiving domain too. Gmail, Outlook and Yahoo form independent opinions, and it is normal to be doing fine at one and badly at another. An aggregate number hides that completely.

If it goes wrong

If placement drops mid-ramp, go back a step and hold there instead of pushing through. The drop means you moved faster than trust accumulated, and it recovers with time at the lower volume.

And if you are ramping because you were forced off a shared domain after an incident, you may be warming a new domain while the underlying provider account still carries the old reputation.