Rate limits

Three things limit what an account can do, and the effective limit is always the lowest of them: the plan, the trust tier, and the per-minute rate limit.

Per plan

Receiving is free on every plan, because charging for the thing that makes an inbox valuable would be the wrong business.

Every number above is read, as this page renders, from the same module the API enforces them from — so this table cannot describe a limit the product does not apply. It used to claim that while being a hand-written table that did not.

Programmable addresses and daily sends are a ceiling, not an allowance. A trust tier grants a share of the number above. A new account starts with the share in the start column, which is a fifteenth; ordinary standing is a third, and an established account gets all of it.

Trust, which is not the plan

A brand-new domain cannot be made trustworthy overnight. A new account starts well below its plan's daily allowance and earns its way up as its mail is delivered and read, rather than being handed a large limit it could burn its reputation with on the first day.

Verifying your domain raises it. So does time, and so does mail that arrives without being reported. Nothing you can do makes it instant, and a product that claimed otherwise would be selling you a blocklisting.

Rate limits

Per minute, per account, across every key.

A refusal tells you when to come back. Being refused carries Retry-After in seconds and the daily allowance alongside it, so a client that has hit a limit never has to guess how long to wait:

Retry-After: 85783
X-RateLimit-Limit-Day: 6
X-RateLimit-Remaining-Day: 0
X-RateLimit-Reset-Day: 1792170122

The send allowance is a rolling twenty-four hours, not a calendar day, so X-RateLimit-Reset-Day is when your oldest send ages out of the window — which is the only honest answer and is why it is a header rather than a rule you could work out yourself.

Every authenticated success also carries X-RateLimit-Limit, -Remaining and -Reset for the per-minute ceiling, so a client can pace itself rather than find the limit by hitting it (the headers).

When you hit one

An entitlement refusal is a 402 with a sentence naming the limit and the alternative — routing an extra address into an inbox you already have is free, and is usually what somebody at the mailbox limit actually wanted.