Both platforms will send cold email, and for most B2B campaigns the choice between them is a small one.
Google Workspace lets one user send 2,000 messages a day, to at most 2,000 unique external addresses. Microsoft 365 allows 10,000 recipients per mailbox a day at up to 30 messages a minute, under a tenant-wide cap on external recipients that grows with your license count.
I plan for about 30 cold emails a day from a warmed mailbox. At that pace neither ceiling comes anywhere close. What actually separates the two is smaller: the price of a mailbox, how Microsoft treats a brand-new tenant, and how many mailboxes your monthly target needs.
I checked every limit, rule and price on this page against Google's and Microsoft's own documentation in September 2026.
Workspace and Microsoft 365 limits side by side
Official per-mailbox limits from Google's Workspace sending limits page and Microsoft's Exchange Online limits page, checked September 2026.
| Limit | Google Workspace | Microsoft 365 (Exchange Online) |
|---|---|---|
| Daily cap per mailbox | 2,000 messages | 10,000 recipients |
| External addresses per day | 2,000 unique (3,000 counting repeats) | No separate mailbox cap (a planned one was canceled) |
| Recipients on one message | 2,000, of which at most 500 external | Adjustable, up to 1,000 |
| Sending speed | Not set on the limits page | 30 messages a minute |
| Tenant-wide cap | Not on the limits page | Yes, based on your license count |
| Trial accounts | 500 messages a day | Lower tenant cap for trial tenants |
| Over the limit | Sending stops for up to 24 hours | Mailbox waits until its 24-hour count drops |
| Same on every business plan | Yes | Yes |
For cold email, the row that binds on Google is the 2,000 unique external addresses, because every prospect is a new external address. On Microsoft the 10,000 per mailbox almost never binds. The tenant cap can.
I read both columns as the most a provider will put up with before it refuses, and nothing more. They are anti-abuse ceilings, there so that one hijacked account cannot flood the internet overnight. None of them tells you what the receiving inbox will accept. That is a separate question, and inbox placement data split by provider is the nearest thing to an answer.
Microsoft says as much about itself. Outside a separate high-volume product, its own Exchange team writes that "Exchange Online doesn't support bulk or high-volume email". Google's page adds that its limits "can change without notice".
Microsoft's tenant cap, and the limit it dropped
The Tenant External Recipient Rate Limit caps how many external recipients your whole Microsoft tenant can reach in a sliding 24 hours, across every mailbox in it. The formula is 500 times your number of paid email licenses to the power of 0.7, plus 9,500.
In Microsoft's own sample table, 1 license gets 10,000 external recipients a day, 10 licenses get 12,006 and 25 licenses get 14,259. Past the cap, external mail from the whole tenant bounces with error 550 5.7.233 until the 24-hour count falls.
Two details matter for anyone opening a new tenant for cold email:
- New tenants start at a fraction. Microsoft's August 2026 update, rolling out from September 14, 2026, gives a tenant 10% of its calculated quota for its first 30 days and 25% from day 31 to day 60.
- The default domain is nearly useless. Mail sent from the default onmicrosoft.com address is limited to 100 external recipients a day for the whole organization, so your own sending domains go in before anything else.
You may also still read about a 2,000 external recipient limit per Microsoft mailbox. Microsoft announced it in April 2024 as a sub-limit inside the 10,000, with enforcement later scheduled to start in April 2026.
On January 6, 2026, Microsoft canceled that limit indefinitely after customer feedback, and confirmed that the 10,000 recipient limit and the tenant cap stay as they are.
At least one cold email tool's comparison guide that still ranks for this question lists the 2,000 figure as a live limit, so check the date on any page that quotes it.
Why published safe volumes run from 25 to 500 a day
The official ceilings answer what the platform allows. What a founder actually needs to know is how much one mailbox can send before inbox placement starts to slip, and the published answers are far apart.
Woodpecker, which sells cold email software, lists 100 to 150 a day as a safe outreach volume on Google Workspace and 200 to 500 on Microsoft 365, and warns that accounts can get blocked long before they reach the official limit.
Unify, another outbound software vendor, puts the cap experienced teams use on a fully warmed mailbox at around 25 to 65 a day, with no split by provider. Both sell software, so read these as vendor guidance.
The spread has causes. What one mailbox can carry moves with the age of the domain, how long the mailbox has existed, whether people ever reply to it, how many other mailboxes share its domain, and how strict your prospects' filters are that month. A single published figure blends all of that into one number.
So I take the bottom of the range. About 30 a day per warmed mailbox, and not past 40 unless I can explain exactly why.
In one real client month from our sending setup, 20 addresses carried roughly 25 emails a day each. Per-mailbox volume is the last number I raise, and only once the warm-up is done.
Turning 2,500 people a month into a mailbox count
Work backwards from the people you want to reach. Say 2,500 new people a month, three emails each:
- 2,500 people x 3 emails = 7,500 sends a month.
- Over about 22 working days, that is roughly 341 sends a day.
- Add 20% headroom, because this month's follow-ups land on top of next month's first emails. That makes about 409 sends a day of capacity.
- Divide by what you trust one mailbox to carry, and round up.
| Daily sends per mailbox | Where the figure comes from | Mailboxes for 409 a day |
|---|---|---|
| 2,000 or 10,000 | Google's or Microsoft's official ceiling | 1 |
| 200 to 500 | Woodpecker, Microsoft 365 | 1 to 3 |
| 100 to 150 | Woodpecker, Google Workspace | 3 to 5 |
| 25 to 65 | Unify, any provider | 7 to 17 |
| 30 | My planning figure | 14 |
The same target needs one mailbox or seventeen, depending on whose number you believe. That spread is the real decision here, and neither platform's pricing page makes it for you.
Microsoft's tenant cap counts every external recipient the whole tenant reaches, so it follows your total daily sends, whichever way you split them across mailboxes. At 409 a day it never binds. Even in a tenant's first 30 days, at 10% of its quota, 1 license allows 1,000 external recipients a day, 3 allow about 1,060 and 14 allow about 1,270.
It starts to bind when a young tenant tries to reach more than about 1,000 people a day, roughly 2.5 times this example. A team that wants to launch big on a brand-new Microsoft tenant hits that wall in its first month. Past day 60, even a single-license tenant gets 10,000 a day.
Whichever platform you choose, none of those mailboxes writes to a prospect until it has warmed up for 10 to 14 days. That is one reason the first weeks of an outbound engagement look so quiet.
What a mailbox costs on each platform
List prices per user per month on Google's pricing page and Microsoft's business plan comparison, September 2026. Google's page showed euro prices and Microsoft's US page dollars; both vary by country.
| Plan | Per mailbox per month | 14 mailboxes |
|---|---|---|
| Google Workspace Business Starter | EUR 6.80, billed monthly (16% less on a one-year commitment) | EUR 95.20 |
| Google Workspace Business Standard | EUR 13.60 | EUR 190.40 |
| Microsoft 365 Business Basic | $7.00 paid yearly, or $5.40 without Teams | $98.00, or $75.60 |
| Microsoft 365 Business Standard, Copilot included | $23.50 paid yearly | $329.00 |
The sending limits are the same on every business plan on both platforms, so the entry plan does the job for a mailbox that only sends and receives cold email. The higher tiers buy other features, not sending room.
Google's page also shows time-limited promotional prices. Budget on the list price, alongside the data, verification and sending tools the rest of the stack needs.
Gmail and Outlook rules apply whichever you buy
Your platform's limits govern what leaves your mailbox. A second set of rules governs what the prospect's provider accepts, and those rules are the same whether you send from Workspace or Microsoft 365.
Google wants SPF or DKIM on mail from any sender, and spam complaints kept under 0.3%. Past 5,000 messages a day into Gmail inboxes, it also requires DMARC, domain alignment and one-click unsubscribe.
Microsoft draws its line at 5,000 messages to Outlook.com, Hotmail and Live addresses from one From domain, with SPF and DKIM passing and a DMARC record of at least p=none.
A 14-mailbox campaign sits far below both thresholds. I still put SPF, DKIM and DMARC on every sending domain before the first send, whatever the volume. The setup post linked above shows where those records fit in the full build.
Which one fits your setup
| Your situation | What decides it | Where it points |
|---|---|---|
| About 30 a day per mailbox | Neither ceiling applies | Either. Pick on price and on which admin console your team already knows |
| Hundreds a day per mailbox | Both allow it on paper, but it sits above Unify's range and far above my 30 | Neither. Add mailboxes instead |
| New tenant, launch within 60 days, high volume | Microsoft's reduced quota for young tenants | Workspace, or keep Microsoft volume low |
| Many mailboxes on one Microsoft tenant | The tenant cap is shared by all of them | Watch the tenant outbound report in the Exchange admin center |
| Starting on a free trial | Google trials cap at 500 a day; Microsoft trial tenants get a lower tenant cap | Pay for the plan |
Interface and automation barely enter it. The mailboxes get connected to your sequencing tool, which does the sending, so the admin console is somewhere you spend time during setup and rarely after.
Smirnov Consulting Group is a Prague-based B2B outbound lead generation agency that runs cold email and LinkedIn campaigns for founder-led B2B companies and books qualified sales calls. In that work, the mailbox provider is one of the smaller decisions. The mailbox count, the warm-up and the list carry far more weight, and most cold email problems start with the list.
Questions about Workspace and Microsoft 365 for cold email
Can I use Google Workspace and Microsoft 365 at the same time for cold email?
Yes, on different sending domains. Each domain's mailboxes live with one provider, because a domain's MX records can point its incoming mail to only one provider at a time. The per-mailbox volume you plan for applies the same way on both.
Is Microsoft's 2,000 external recipient limit still coming?
No. Microsoft canceled the mailbox external recipient limit indefinitely on January 6, 2026. The 10,000 recipients per mailbox per day and the tenant-wide cap on external recipients stay in place.
Does a more expensive plan raise the sending limit?
No. Google applies the same limits across its Business, Education and Enterprise editions, and Microsoft lists 10,000 recipients a day and 30 messages a minute for Business Basic, Standard and Premium alike.
Can I send cold email from a trial account?
You can, but trial limits are lower on both platforms: 500 messages a day on a Google trial, and a reduced tenant cap on a Microsoft trial tenant. A new mailbox should spend its first 10 to 14 days warming up rather than writing to prospects anyway.