How many cold emails per day per mailbox? Hard limits versus vendor ranges

Cold emails per mailbox per day: the short answer

For a warmed-up mailbox, most guides suggest 20 to 50 cold emails per day, and a new mailbox should start at roughly 5 to 10.

There is no official number. Google and Microsoft publish hard ceilings far above what a cold email program should send, and vendors publish opinions that run from 8 to about 100 a day per mailbox. Below, the published limits sit beside the vendor ranges, followed by a ramp-up schedule, send spacing and stop rules.

FoxKnock sends from your own mailboxes, so we have a stake here: treat our defaults as opinions.

Cold email sending limits: what Google and Microsoft publish

Both providers publish limits to stop abuse and compromised accounts, not to guide outreach.

Google Workspace

• For one-recipient cold emails, the tightest figure is about 2,000 messages a day. The page does not say whether mail sent through a third-party tool over SMTP counts as mail merge, so if you plan near the ceiling, assume the lower 1,500.
• Trial accounts stay at the trial limits until the domain has paid at least $100 in total, and the increase can take up to 75 days after that.
• Google's page was last updated on 2026-10-13 and says all limits can change without notice.

Microsoft 365

• The per-mailbox limit is 10,000 recipients in a sliding 24 hours.
• Microsoft also caps a whole tenant. The daily limit on external recipients is 500 times the number of paid email licenses raised to the power 0.7, plus 9,500. One license gives 10,000 and ten give about 12,006. When the tenant cap is hit, every user in the tenant is blocked from emailing outside.
• Mail from a default onmicrosoft.com address is limited to 100 external recipients per organization per 24 hours.
• New and trial tenants get less. A Message Center notice (MC1454397, updated 2026-09-29) says that, in a rollout running from mid-September to the end of November 2026, tenants under 31 days old get 10% of the calculated quota and tenants 31 to 60 days old get 25%, and trial tenants drop from 5,000 external recipients a day to 500. Microsoft's limits pages still listed 5,000 for trials when we read them on 2026-10-17, so check the Tenant Outbound External Recipients report in your own tenant.

What neither provider tells you

• No safe cold email number. Microsoft says Exchange Online is not designed for bulk mailing and points bulk senders to specialist services. Its own advice for bulk mail through Microsoft 365 includes a custom subdomain, spreading sends over time and staying under 30 messages a minute per mailbox.
• Policies that cover cold email loosely. Google's Cloud Acceptable Use Policy, which covers Workspace, bars using the service for unsolicited mass email, and Google's spam policy says it can suspend a user and, when a problem is domain-wide, the whole account.
• No line between outreach and mass email. Neither policy says where targeted one-to-one outreach ends and mass email begins. That is one reason many guides tell you to keep cold email off your main domain.

Gmail's sender rules apply too. Everyone sending to personal Gmail addresses needs SPF or DKIM and a spam rate under 0.3% as reported in Postmaster Tools (more under the stop rules below). Google's FAQ describes a bulk sender as one that sends close to 5,000 or more messages in 24 hours to personal Gmail accounts (the guidelines page says more than 5,000). Messages from one primary domain are counted together, and bulk-sender status has no expiration date once assigned. Small teams sit far below that line.

What vendors recommend, and why the numbers differ

We read these on 2026-10-17. All come from companies that sell sending tools or mailboxes.

The spread is more than tenfold, so the numbers cannot all describe the same thing. They assume different mailbox types, warm-up routines and list quality. Vendors that sell mailboxes or sending capacity also gain when you spread volume across more of them. That does not make the advice wrong, but it is a reason to read it as opinion.

Two details help:

• Smartlead reports that the median mailbox on its platform sends 14 cold emails a day, well under its own 50 (its own data, which we could not check).
• Email Awesome, a vendor of email verification and warm-up tools rather than sending, argues that a figure such as 30 or 50 per inbox is not a universal rule from mailbox providers, and that a plan should start from permission, relevance and delivery feedback.

Email warm-up schedule: how to ramp a new mailbox

Google's guidance for raising volume is consistent:

• Start low, with engaged recipients.
• Increase slowly and avoid sudden spikes, such as suddenly doubling previous volume.
• Send at a steady rate instead of in bursts.
• Send daily rather than weekly, which lets you ramp faster.
• If messages start bouncing or being deferred, reduce volume until the SMTP error rate falls, then climb again slowly.

Part of that advice is addressed to senders of large volumes, but the daily-versus-weekly point applies to any sender, and the logic holds at small scale.

Vendor schedules agree on the shape and differ on the numbers. Cold emails per day, by week of a new mailbox:

Each source qualifies its own table. Another passage on Instantly's page says to start at 5 to 10 a day in week one. Unify calls its figures directional. A safe-range section of the Inboxlogy post says 5 to 15 for weeks 2 and 3.

Warm-up networks, which exchange automated messages between members' mailboxes, are a separate question. Instantly recommends them (it runs one) and Unify advises skipping them. The Google and Yahoo pages we read say nothing about them, and we found no independent test of whether they help; the placement figures we came across were published by vendors. Either way, a calendar alone is a weak ramp: hold the step if bounces rise.

Turn a number into a daily plan

Count everything a mailbox sends: first emails, follow-ups, manual replies and any warm-up network traffic, which is sent from the same mailbox and so counts toward the provider's limits. Vendors differ here: Maildeck's safe limits exclude warm-up, while Instantly's total of 30 to 40 a day in weeks 3 and 4 includes it.

A hypothetical example: a team runs a three-email sequence (a first email and two follow-ups). In steady state each day carries one first email, one first follow-up and one second follow-up per new contact, so daily sends are about three times the new contacts per day.

• At 25 sends a day, that is roughly eight new contacts a day, or about 40 a week on five sending days (replies and bounces remove a few).
• To start 24 new contacts a day, the team needs about 72 sends, or three mailboxes at 25 each.

More mailboxes and domains: where it helps and where it stops

Spreading volume is sound: if one mailbox has a bad week, the others keep working. But it has limits:

• Reputation is not only per mailbox. Google says Gmail tracks volume, feedback and limits per domain and per IP address, and Postmaster Tools reports your domain's spam rate. So ten mailboxes on one domain add up to one domain's record. Smartlead says each mailbox also carries its own reputation; the Google pages we read describe domain and IP tracking and do not mention a per-mailbox score.
• Subdomains do not reset the count. Bulk-sender status counts messages from the same primary domain.
• Limits and account risk are shared. On Microsoft 365 every mailbox draws on one tenant limit, and, as noted above, a domain-wide problem can put a whole Google account at risk.
• Every domain has a cost. Each needs its own DNS authentication, its own ramp and its own monitoring. See SPF, DKIM and DMARC for cold email.
• Recipients see messages, not mailboxes. Three mailboxes emailing one person, or three people at one company, look like three emails. De-duplicate at the contact and company level (our reasoning, not a published rule).

Spacing between sends

Microsoft throttles SMTP submissions above 30 messages a minute. At that rate 50 emails leave in under two minutes, which is the kind of burst Google tells senders to avoid (Google does not define a burst).

Vendor advice on gaps is thin:

• Saleshandy suggests 60 to 190 seconds between sends.
• Instantly suggests a send window in the prospect's morning (8:30 to 10:30) and warns that 500 emails in an hour from a new inbox looks suspicious.
• Inboxlogy warns against bursts inside a five-minute window.

The arithmetic is gentle. With a 90-second gap (our example, not a published rule), 25 emails occupy 37.5 minutes of send slots and 50 occupy 75, while an eight-hour window holds 320 slots. Spacing does not limit your volume. It removes bursts.

When to stop: bounce and complaint limits

Complaints. Google and Yahoo publish the only provider thresholds we found. Google says to stay under 0.1% and never reach 0.3%, and Yahoo says to keep the spam rate below 0.3%. 0.1% is one complaint per 1,000 messages. A sending tool can only count the complaints that arrive in the mailbox as feedback-loop reports. As industry write-ups describe it, Gmail does not send those and reports spam rate only in aggregate in Postmaster Tools, so watch Postmaster Tools for Gmail.

Bounces. Google, Yahoo and Microsoft give no bounce threshold in the pages we read (Yahoo and Microsoft say to monitor bounces). Vendors do:

• Instantly: 2%.
• Unify: 2% to 3%.
• Inboxlogy: about 3%.
• Smartlead: 4% over 14 days on at least 100 sends, which it says is where inbox providers start routing mail to spam.
• Maildeck: 5%.

That is a 2.5 times gap with no neutral referee.

Small samples are noisy: one bounce in 20 sends is 5%. Set a minimum number of sends before a rule can fire, and when it fires, pause the mailbox rather than slowing it. Then look for the cause: the list source, old data, or catch-all addresses (see catch-all emails).

How FoxKnock handles this

FoxKnock sends only from mailboxes you connect, using an app password over SMTP and IMAP: Google Workspace or any SMTP and IMAP mail server.

Microsoft 365 is limited. Microsoft no longer accepts passwords (Basic authentication) for IMAP in Exchange Online and is retiring it for SMTP AUTH, so a Microsoft 365 mailbox may not connect or may not sync replies. FoxKnock does not offer Microsoft sign-in.

Its defaults:

• 25 sends a day per mailbox, with a hard maximum of 50.
• A ramp that starts at 8 a day (never above 20) and rises in a straight line to the daily limit over 21 days.
• At least 90 seconds between sends from a mailbox.
• Automatic pause when bounces pass 2% of the last 100 sends or complaints pass 0.1% of the last 1,000. Each rule needs at least 20 sends first, and complaints are counted from feedback-loop reports that reach the mailbox.
• A 15-minute back-off when Gmail throttles.
• A confirmation when you put more than three mailboxes on one domain. It is a warning, not a block, and three is our judgment, not a provider rule.

These sit under every provider ceiling above. The default of 25 is at the low end of the 20 to 50 vendor cluster, and the maximum of 50 is at its top. The ramp changes only how many messages go out: FoxKnock has no warm-up network and no inbox-placement testing, and we do not promise placement. See cold email sending, and cold email deliverability in 2026 for the wider picture.

Where this leaves you

1. Pick a number from the cluster that fits your mailbox, and start below it.
2. Ramp over several weeks, and hold a step if bounces rise.
3. Space your sends instead of sending in bursts.
4. Set your stop rules before you launch.

Sending limits are about deliverability, not legality: whether you may email someone at all depends on their country and your relationship with them (see our GDPR cold email guide). This is not legal advice.

If you want to see how this works on your own market, try FoxKnock with the free credits, no card needed.