A warmed mailbox on a dedicated sending domain can carry roughly 20 to 30 cold emails a day. That figure is a per-mailbox ceiling, not a per-company one, and the correct way to send more is to add mailboxes rather than to push any single one harder. Providers also weigh how the sending is distributed: the same 25 messages spread through a working day is a different signal from 25 sent in one burst at nine in the morning.
It is the first question anyone asks when they set up outbound, and it is almost always asked in the wrong unit. The answer is not a number of emails per day for your company. It is a number per mailbox — and once you see it that way, the rest of the design follows.
The number
Twenty to thirty cold emails a day, per warmed mailbox, on a dedicated sending domain. A new mailbox starts far below that, at two or three a day, and reaches the ceiling over roughly three weeks of warming.
The most common objection is that Gmail allows 2,000 messages a day from a Workspace account, so twenty-five sounds absurdly conservative. Both numbers are real; they measure different things. The 2,000 figure is the point at which Google stops you sending. The twenty-five is the point beyond which cold mail starts costing you reputation faster than it earns you replies.
The gap exists because cold mail behaves differently from ordinary correspondence. Normal business email is mostly replies to people who wrote to you, sent to addresses that definitely exist, opened by people expecting them. Cold email is none of those things, so it produces bounce, complaint and non-engagement rates that ordinary mail never approaches. The account limit was never designed with that traffic in mind.
Why the ceiling is per mailbox
Reputation is scored per sending domain and per sending address. Three mailboxes on two domains sending 25 each is 75 messages a day, spread across three reputations that are assessed separately. One mailbox sending 75 is a single address behaving three times as aggressively as a person plausibly would.
This has a useful consequence. Volume becomes a capacity-planning problem rather than a risk decision. If you need to reach more people, you add mailboxes, warm them, and the total rises with no additional exposure on any individual address. Nobody has to decide whether to "push it a bit this week".
It also makes failure survivable. If one address starts producing bounces, you slow or stop that one. The campaign continues at reduced capacity instead of ending.
Working out how many mailboxes you need
The arithmetic is simple enough to do on the back of an envelope:
- One mailbox at 25 a day across about 22 working days is roughly 550 messages a month.
- A sequence is usually two to three messages per person, so one mailbox reaches around 200 people a month.
- Reaching 500 people a month therefore wants two to three mailboxes; 1,000 people wants four to five.
Two mailboxes on each of two or three domains is a common shape for a small team. Concentrating six mailboxes on a single domain works until that domain has a bad week, at which point everything stops at once.
Distribution matters as much as volume
Twenty-five messages sent between 09:00 and 09:04 and twenty-five spread across a working day carry the same volume and completely different signals. The first is unmistakably automated. The second is what a person doing focused outreach looks like.
Sensible practice is to spread sends across roughly nine hours with irregular gaps, keep to the recipient's working days rather than your own, and avoid the exact top of the hour. None of this is a trick — it is genuinely closer to how the mail would go out if a person were sending it.
Signs you are over the line
The failure mode is gradual, which is what makes it dangerous. Watch for delivery rate drifting below 95 percent, bounces climbing past 3 percent, complaint rate approaching 0.3 percent, reply rates falling on copy that has not changed, or mail that used to reach the inbox now landing in Promotions. Any one of these on a single address is a reason to slow that address this week rather than next month.
What this means in practice
A safe outbound programme is not one big sender. It is a pool of modest, individually monitored mailboxes, each doing a small amount of work, with capacity added by adding mailboxes and problems handled by quietly reducing one of them.
That is a genuinely tedious thing to run by hand, which is why most teams set the limits once and never look again. Operater's Sales agent holds every mailbox to its own ceiling for the day, paces the sends through the recipient's working hours, and watches each address separately — slowing one and moving its share to the others when the numbers move, so the campaign finishes a little later instead of stopping. You never set a daily limit, because it is not a number anyone should be tuning by feel.
Key takeaways
- Twenty to thirty a day per warmed mailbox is the working ceiling for cold outreach.
- Scale by adding mailboxes, never by raising a single mailbox's limit.
- Provider account limits are far above the safe limit. They are not the constraint that matters.
- Timing and spacing are part of the signal, not a nicety.