Sending limits
comail caps how fast you can send. Two limits apply to every message, and the relay enforces whichever one is stricter.
The two limits
Section titled “The two limits”- Per-domain warming. Every domain you enroll starts cold and earns volume over its first two weeks. Each domain warms on its own clock, independent of any other domain on your account. See Warming tiers for the schedule and caps.
- Account ceiling. A per-account (per-DID) cap on your total send rate across every domain you’ve enrolled. By default the ceiling is 50 messages per hour and 500 per day.
Your effective limit for any send is the lower of the two. A brand-new domain on an otherwise-warmed account is still held to the warming cap; a fully warmed domain is still held to your account ceiling.
What counts
Section titled “What counts”Both limits count messages submitted to the relay, whether they later deliver, bounce, or defer. A multi-recipient message counts once per recipient. The account ceiling sums across all of your domains, since send activity is tracked per-DID.
When you hit a limit
Section titled “When you hit a limit”The relay rejects the message with 429 (HTTP API) or 451 (SMTP). Wait for the window to reset and retry. Your current usage is visible at /account under the deliverability section; your configured hourly and daily limits are also returned by GET https://smtp.atmos.email/member/status?did=....
Founding members
Section titled “Founding members”comail’s founding alpha grants early members a permanent, higher entitlement:
| Standard account | Founding member | |
|---|---|---|
| Hourly ceiling | 50 / hour | 100 / hour |
| Daily ceiling | 500 / day | 1,000 / day |
| Sending domains | 1 | up to 3 |
Founding status is an account entitlement. It preserves the higher limits when another account setting would otherwise lower them. Check your account for the limits that apply to you.
The founding window ended on June 15, 2026 at 07:00 UTC. Existing grants remain visible in the account console; new members should not expect a founding grant.
Per-domain warming still applies to founding members. The higher account ceiling lifts your steady-state rate, but each new domain you add still warms from cold.
Paid plans
Section titled “Paid plans”Check the account console for your current entitlement and available offers. A plan or credit balance does not remove a new domain’s warming limits. Use the hourly and daily limits returned for your account when scheduling sends.