Warming tiers
New domains start with lower sending limits. These limits increase as the domain moves through its warming period.
Why warming exists
Section titled “Why warming exists”comail members share an IP pool. A new domain that immediately sends thousands of messages could damage the pool’s reputation for everyone. Warming tiers cap outbound volume for new members so mailbox providers (Gmail, Outlook, Yahoo) can build a positive association with your domain gradually.
The three tiers
Section titled “The three tiers”| Tier | Duration | Hourly cap | Daily cap |
|---|---|---|---|
| Warming | Days 0–7 | 2 / hour | 10 / day |
| Ramping | Days 7–14 | 10 / hour | 50 / day |
| Warmed | Day 14+ | No tier cap | No tier cap |
Caps apply per-domain at submission time. The Warmed row has no warming cap, but your account ceiling still applies. If you hit a limit, the relay returns a 429 (HTTP API) or 451 (SMTP). Retry after the window resets.
What counts toward the cap
Section titled “What counts toward the cap”Caps measure messages submitted to the relay. Whether a message ultimately delivers, bounces, or defers downstream doesn’t change the count. Multi-recipient messages count once per recipient.
Warming is per-domain
Section titled “Warming is per-domain”Each domain warms on its own clock. The relay uses the domain’s recorded warming start, or its creation date if no warming start is set. An operator can adjust the start or set a tier override. A second domain normally begins cold even if your first domain is fully warmed.
Your account also has an overall send ceiling that spans every domain. The relay enforces whichever limit is stricter. See Sending limits for how the two combine and what founding members get.
Tier progression
Section titled “Tier progression”Without an override, tiers advance automatically from the domain’s warming start. Check your current tier and limits in the account console.
Tips for a clean warm-up
Section titled “Tips for a clean warm-up”- Send to engaged recipients first: real users who expect your mail.
- Avoid bulk sends during the first week. Spread volume across hours.
- Monitor bounces and complaints at /account. High complaint rates can lead to suspension.
- Make sure your DNS records (DKIM, SPF) are correct before sending. The relay checks these on enrollment.