How Many Cold Emails Per Day? A Plan for One Mailbox

How many cold emails a day can one mailbox send?

For a small business with one warmed-up mailbox, start at about ten new cold emails a day and raise the number by five a week, only while bounces and complaints stay near zero and people still reply. That is my working rule for one mailbox, not a rule from any provider. Google Workspace lets a user send 2,000 messages a day and Microsoft 365 allows 10,000 recipients a day, but those are the points at which the provider stops your mailbox, not the points at which cold email still lands in the inbox. For a sender of one or two mailboxes, the safe number is set by the quality of the list and the replies it gets. This guide gives a weekly plan for one mailbox and for two, the three signals to watch, and the rule for when to raise or cut the number.

Start low and earn every increase. This is the plan I would follow for one mailbox on its own domain, once the four week warm-up is done and the ordinary business mail is still going alongside the cold mail.

Week one. New cold emails a day, one mailbox: 10. New cold emails a day, two mailboxes: 10 from the first mailbox only. What has to be true before moving on: No more than one or two addresses in a hundred bounced. No complaints. Test messages land in the inbox.

Week two. New cold emails a day, one mailbox: 15. New cold emails a day, two mailboxes: 15 from the first, 10 from the second. What has to be true before moving on: The same three checks, now for each mailbox separately.

Week three. New cold emails a day, one mailbox: 20. New cold emails a day, two mailboxes: 20 from the first, 15 from the second. What has to be true before moving on: Replies are still coming in at about the rate they did in week one.

Week four. New cold emails a day, one mailbox: 25. New cold emails a day, two mailboxes: 25 from the first, 20 from the second. What has to be true before moving on: Every check above still holds.

Week five onwards. New cold emails a day, one mailbox: Up to 30, and only higher if every signal stays clean for a further week. New cold emails a day, two mailboxes: Up to 30 from each. What has to be true before moving on: Weekly check of the three signals, every week, before any increase.

The numbers count new people contacted each day. Follow-ups come on top of them, and the last section of this guide shows what that does to the daily total. Weekends are left out: send on working days, when the people you write to are at their desks in Ireland and the UK.

B2B email outreach: a practical guide for small businesses

Why is the provider limit not the safe limit?

A provider limit is a ceiling the provider enforces on everyone, whatever they send. Google Workspace allows 2,000 messages a day per user and 3,000 external recipients a day, and only 500 messages a day during a free trial. Reach one of those limits and the user cannot send new messages for up to 24 hours (Gmail sending limits in Google Workspace, read 2026-10-22). Exchange Online, the mail service in Microsoft 365, allows 10,000 recipients a day and 30 messages a minute per mailbox. Microsoft says the recipient limit exists to discourage the delivery of unsolicited bulk messages, and that customers who need to send legitimate bulk commercial email should use specialist providers (Exchange Online limits, read 2026-10-22).

None of those figures says how many cold emails will reach an inbox. Inbox placement is decided by the receiving side: whether recipients open, reply, ignore or report your messages, whether the addresses exist, and whether the volume suddenly jumps. Gmail's guidance to senders is to start with a low volume to engaged recipients, increase it slowly, and avoid sudden spikes if you have no history of sending large volumes (Gmail email sender guidelines, read 2026-10-22). A mailbox can stay well inside its provider limit and still be sending most of its cold mail to spam.

The managed B2B Email Outreach service page on this site says up to 500 emails a day per email account, once the account is ready and limits allow. That is an upper bound the service works under, set by the sending setup, not the number a new mailbox starts at. The plan above is how a single small business mailbox gets anywhere near a figure like that, and many never need to.

What signals decide whether to send more or less?

Three signals, read once a week for each mailbox:

Bounces. Count the cold emails that came back as undeliverable. Every bounce is a message to an address that does not exist, and a run of them tells the receiving servers the list was not checked. My working rule is to stop and check the list if more than two addresses in a hundred bounce in a week.

Complaints and spam placement. Any reply asking how you got the address, any reply saying the message went to junk, and the placement of a test message sent each week to a Gmail address and an Outlook address you control. Gmail asks every sender to keep the spam rate in Postmaster Tools below 0.3 percent and recommends staying below 0.10 percent (Gmail email sender guidelines, read 2026-10-22). Postmaster Tools may show no data at low volume, which is why the test messages matter.

Replies. Positive, negative or a polite no, a reply means the message reached a person and was read. Compare each week with the first week of cold sending. A falling reply rate with an unchanged email and list usually means more messages are landing in spam.

The rule that goes with them:

Raise by five a day only after a full week in which all three signals were clean.
Hold the number if one signal is borderline: a bounce rate near the limit, one complaint, or a test message landing in promotions.
Cut the number in half if bounces pass the working limit, a test message lands in spam, or replies drop sharply. Fix the cause first: check the list, look at the email itself, confirm SPF, DKIM and DMARC still pass.
Stop all cold sending if the provider blocks the mailbox or bounces start arriving for most messages. Gmail's guidance is to reduce sending volume when messages start bouncing or being deferred.

How does a second mailbox change the plan?

A second mailbox doubles the capacity, not the speed. It needs its own warm-up and its own ramp, and it starts a week after the first, as the table shows, so a problem shows up in one mailbox before it reaches both.

Split the list, never duplicate it. Each person is contacted from one mailbox only. Two cold emails from two addresses at the same business is the quickest route to a complaint.
Read the signals per mailbox. A combined bounce rate hides a problem in one of them.
Use a second domain with care. Two mailboxes on your main business domain share that domain's reputation, so a problem on one affects the mail that carries your invoices and client work. One way round it is a separate domain for cold outreach, clearly linked to the business, with the main domain kept for ordinary mail.
Keep both mailboxes real. Each one needs a person's name, a plain signature and replies that get answered.

What breaks a mailbox fastest?

An unchecked list. Old, bought or guessed addresses bounce. Verify every address before it goes into a campaign.
A sudden jump. Going from ten a day to a hundred because a new list arrived. Gmail warns against sudden volume spikes and asks senders to send at a consistent rate, not in bursts.
Missing authentication. Gmail requires SPF or DKIM from every sender, and recommends SPF, DKIM and DMARC on every domain. A record that stopped passing after a DNS change sends everything to spam from that day on.
An email nobody wants. A generic message to the wrong people gets ignored or reported, and reports cost more than silence.
Links and attachments in the first email. Keep the first message plain: no attachment, and at most one link that is visible and clear about where it goes.
Sending without permission. Who you may email depends on the country and on whether the address belongs to a company or an individual. Ireland and the UK have their own rules, and they apply from the first email. The Irish guide on this site sets out the rules for B2B cold email in Ireland.

How does this fit a campaign that follows up two or three times?

Follow-ups are emails too, and they count toward the day. If a mailbox contacts 20 new people a day and each one gets two follow-ups a few days apart, the mailbox is sending about 60 cold emails a day once the campaign has run for a couple of weeks: 20 first emails, 20 first follow-ups and 20 second follow-ups. With three follow-ups it is about 80.

So set the daily number for new contacts with the follow-ups in mind:

Count the total, not the first emails. The signals in the earlier section apply to everything the mailbox sends.
Stop following up anyone who replied, including a no, and anyone whose email bounced.
Leave a few working days between messages to the same person, and stop after the last planned follow-up.
Keep the ordinary mail going. A mailbox that only sends cold mail and never receives a normal reply looks less like a business mailbox every week.

Common questions about daily cold email limits

Is Google Workspace or Microsoft stricter with cold email? Neither publishes a cold email limit, and the published limits differ in what they count. Google Workspace counts messages and external recipients per user per day, 2,000 and 3,000, and blocks sending for up to 24 hours when a limit is reached (Gmail sending limits in Google Workspace, read 2026-10-22). Exchange Online counts recipients per day, 10,000, and messages per minute, 30, and Microsoft states that its limits exist to discourage unsolicited bulk mail. Both limits sit far above any safe cold sending number for one mailbox, so the practical limit on either is the one set by your signals.

Do replies count toward the limit? Toward the provider limit, yes: every message the mailbox sends counts, including replies, follow-ups and ordinary business mail. Toward the cold sending plan, no: the plan counts new people contacted each day. Replies to people who wrote to you are good for the mailbox, so answer them promptly.

Should I send everything at once or spread it through the day? Spread it. Gmail asks senders to send at a consistent rate and avoid bursts. A sending tool can space messages a few minutes apart through the working day. If you send by hand, send in small batches through the morning and early afternoon, in the recipient's time zone.

What bounce rate is too high? Neither Google nor Microsoft publishes a bounce rate for cold email. Gmail's guidance is to reduce sending volume when messages start bouncing or being deferred, and to unsubscribe recipients who have bounced more than once. My working rule for one mailbox is that more than two bounces in a hundred cold emails in a week means the list needs checking before anything else is sent, and any bounce from an address that was never verified means the verification step was skipped.

When a managed service makes sense

If you want the sending run for you, B2B Email Outreach is €450 a month, with the sending tool and the inbox warm-up tool included and contact lists separate. Month one is warm-up, sending starts from month two on the schedule agreed with you in writing, and people who have not replied get two or three polite follow-ups. If your domain is not set up yet, Email Setup is €75 one-time per domain (the pricing page, read 2026-10-22).

To start, send a short written brief through the contact page, and I confirm the scope in writing before any payment.

Sources

Email sender guidelines, from Gmail Help (opens in a new tab) — checked 2026-10-22
Gmail sending limits in Google Workspace, from Google Workspace Help (opens in a new tab) — checked 2026-10-22
Exchange Online limits, from Microsoft Learn (opens in a new tab) — checked 2026-10-22