Sending Limits and Domain Warm-Up: Why New Domains Get Filtered

Sending limits read like an arbitrary tax right up until you understand what they prevent. A brand-new domain that sends four thousand messages on its first afternoon is, from a receiving server's point of view, indistinguishable from a compromised account being used by whoever compromised it. Receivers treat both the same way, and the way they treat them is badly.

So the caps aren't there to sell you an upgrade. They're there because the alternative — letting a new domain send at full volume immediately — reliably damages the thing you were trying to use.

Here's what the sending limits are, what happens when you hit one, and how to ramp a new domain without getting filtered.

What Sending Limits Actually Protect

Two things, and only one of them is yours.

Your domain's reputation. Gmail, Outlook and Yahoo build a picture of every sending domain over time: volume, consistency, complaint rate, bounce rate, engagement. A domain with no history that suddenly sends thousands of messages sets off exactly the pattern used to detect a hijacked account. The filtering that follows applies to all your mail, including invoices and password resets.

Everyone else on the same infrastructure. Outbound mail from a shared platform leaves from shared IP addresses. One account sending a burst of unsolicited mail degrades delivery for every other account on that IP. Sending limits are how a platform stops one customer's bad week becoming everyone's.

Neither of those is negotiable by raising a limit. They're properties of how receiving servers judge senders, and no configuration on the sending side changes them.

The Limits by Plan

Three separate sending limits, and they interact. The mailbox limit is what one address can send in 24 hours. The account limit is everyone combined — twenty mailboxes on Starter can't each send 1,000, because the account ceiling is 6,000. Recipients per message counts To, Cc and Bcc together, so one message to 120 people breaches Starter's limit even though it's a single send.

There's also an hourly submission cap, which matters for automated sending. A script that fires its entire daily allowance in ninety seconds hits the hourly limit first — and that's the correct outcome, because burst sending is itself a signal receivers dislike.

Why New Accounts Start Lower

Accounts that haven't completed a payment run under reduced sending limits: 30 messages per mailbox per day, 50 across the account, 10 recipients per message, 15 messages per hour. These apply to managed sending and lift automatically once a first payment goes through.

The reason is unglamorous. Free trials on email platforms attract people who want to send one large batch of unsolicited mail and leave, and the cost of that lands on the IP reputation shared by paying customers. A payment is a weak signal of intent, but it's a signal, and the limits it unlocks are immediate.

For genuine evaluation, 30 messages a day is enough to test setup, delivery and mail-client configuration. It isn't enough to run a campaign, which is the point.

What Happens When You Hit a Sending Limit

Sending is refused with an explanatory error rather than accepted and dropped. That distinction matters: a message that's rejected at submission is a message you know about, and one that's accepted and silently discarded is a message you find out about when a customer asks why you never replied.

The counters are rolling, not calendar-based. Hitting the daily limit at 4pm doesn't mean waiting until midnight; capacity returns as the oldest messages age out of the window.

If you're hitting sending limits routinely, there are three real options and one that isn't. Upgrade, if the volume is legitimate and growing. Route bulk mail through a dedicated provider using custom SMTP, which is the right architecture for anything campaign-shaped. Or reduce volume, which is more often the correct answer than people expect — a daily digest instead of eleven notifications is better for the recipient too.

The option that isn't real: spreading the same volume across more mailboxes to stay under the per-mailbox cap. The account limit catches it, receivers see the same domain either way, and it looks precisely like what a compromised account does.

Domain Warm-Up

A new domain has no sending history. Receivers have nothing to judge it by, so they judge it cautiously — which means a fresh domain sending real volume on day one lands a meaningful share of it in spam, regardless of content quality.

Warm-up fixes this by starting small and increasing gradually while the domain accumulates a record of mail people actually want. A workable shape:

Warm-up matters when the domain has never sent email, when it's been dormant six months or more, or when you're arriving from another provider with a large list. You can usually skip it for a domain that's been sending steadily for years and is simply changing host — the reputation attaches to the domain, not the infrastructure.

Two rules make more difference than the schedule. Send to engaged recipients first, because opens and replies are the signals that build reputation fastest. And clean the list before you start — bouncing on a new domain is the single worst thing you can do to it, which is what email verification is for.

What Receivers Are Actually Measuring

Volume is the least interesting input. What moves the needle:

Complaint rate. The share of recipients marking your mail as spam. Google's sender guidelines put the target below 0.1% and treat 0.3% as a hard problem. That's three complaints per thousand — a tiny number, and easy to exceed with a list you didn't build yourself.

Bounce rate. Hard bounces to nonexistent addresses are the clearest evidence of a purchased or stale list. Above 2% is trouble.

Authentication. SPF, DKIM and DMARC are prerequisites, not optimisations. Get them right before worrying about volume — no warm-up schedule compensates for failing authentication.

Consistency. A domain sending 500 messages daily looks healthier than one sending 3,500 every Monday and nothing else, even though the totals match.

Engagement. Opens, replies and non-deletions. This is the input you can't fake and the one that matters most.

Staying Under the Sending Limits

Separate transactional from bulk. Password resets and invoices must arrive. Newsletters would like to. Sending both from one domain means a bad campaign takes your password resets down with it. Use a separate domain or subdomain for bulk, and keep the transactional one clean.

Watch the recipient count. Announcements to a large internal list breach the per-message recipient limit long before the daily one. Send in batches, and use Bcc so recipients don't see each other's addresses.

Spread automated sending across the day. Hourly caps exist, and a nightly job that dumps everything in one burst is the classic way to hit one.

Suppress bounces immediately. Repeatedly mailing an address that hard-bounced is the fastest route to being classified as a bad sender.

Make unsubscribing trivial. Someone who can't find the unsubscribe link clicks the spam button instead, and a complaint costs far more than a lost subscriber. See what happens on the receiving end.

Frequently Asked Questions

What are the daily sending limits?

200 per mailbox and 400 per account on Nano; 1,000 and 6,000 on Starter; 2,000 and 15,000 on Pro; 2,500 and 40,000 on Agency. Recipients per message run from 50 to 500 across the same plans.

Why are my sending limits lower than my plan says?

Accounts that haven't completed a payment run under reduced safety limits — 30 per mailbox per day, 50 per account. They lift automatically once the first payment goes through.

What happens when I hit a limit?

Sending is refused with an explanatory error. Nothing is accepted and silently dropped, and capacity returns on a rolling basis rather than at midnight.

Can I raise the sending limits?

By upgrading, or by routing bulk mail through your own provider with custom SMTP. Spreading the same volume across more mailboxes doesn't work — the account limit catches it and receivers see the same domain regardless.

Do sending limits apply if I use my own SMTP provider?

Ours don't apply to mail relayed through your provider; theirs do, and their ramp requirements are usually stricter. Exceeding them tends to get an account suspended rather than rate-limited.

How long does domain warm-up take?

Four to six weeks to full volume is typical. It's driven by engagement rather than the calendar, so a domain sending to people who reply warms up faster than one sending to a cold list.

Do I need to warm up a domain I'm migrating?

Usually not, if it's been sending consistently for years — reputation attaches to the domain, not the host. Warm up if the domain is new, has been dormant six months or more, or is about to start sending far more than it used to.

Does hitting a limit hurt my reputation?

No. The message is refused before it leaves, so receivers never see it. That's the entire point of enforcing the cap on the sending side.