Microsoft 365 and Outlook Sending Limits

A Microsoft 365 (Exchange Online) mailbox can send to 10,000 recipients a day and 30 messages a minute, with up to 1,000 recipients per message. On top of that, the whole tenant has a daily cap on external recipients that depends on how many licenses it has. A consumer Outlook.com account with a Microsoft 365 subscription gets 5,000 recipients a day. None of these is a safe cold email volume: we recommend up to 25 cold emails per mailbox a day.

We make Outreach2day, cold email infrastructure on standard SMTP/IMAP mailboxes. We don't sell Microsoft 365. The numbers below are from Microsoft's own documentation, checked September 2026.

Exchange Online Sending Limits per Mailbox

Microsoft lists the same sending limits for Microsoft 365 Business Basic, Standard and Premium, Microsoft 365 E3/E5 and Office 365 E1, E3/E5 and F3 (Exchange Online limits):

The recipient rate limit is a sliding window, not a daily reset. Microsoft's example: a user who sends to 5,000 recipients at 9:00 AM, 2,500 at 10:00 AM and 2,500 at 11:00 AM hits the limit and "won't be able to send messages again until 09:00 AM the next day."

A distribution group in the organization's address book counts as one recipient. A personal distribution list counts each member.

Outlook Sending Limits per Minute

The 30-messages-a-minute rule is the only per-minute limit Microsoft publishes for mailboxes. What happens above it depends on how you send:

• Over SMTP client submission (how most sending tools connect), messages above the limit "will be rejected and the client will need to retry."

• Otherwise, the excess "will be throttled and successively carried over to the following minutes," which "will typically not block the sender's account."

Microsoft adds that "Exchange Online isn't suited to accommodate bulk-mailing scenarios" and that customers who need to send legitimate bulk commercial email "should use third-party providers that specialize in these services."

Is There a Per-Mailbox External Recipient Limit?

If you have read about a per-mailbox external recipient rate limit (ERR), check the current page. Microsoft's Exchange Online limits page, updated September 2026, lists no per-mailbox limit on external recipients. The external limits it lists apply to the tenant: TERRL, below, and the cap on onmicrosoft.com addresses.

Tenant External Recipient Rate Limit (TERRL)

TERRL is "the maximum number of external recipients a tenant can send to per day (24-hour sliding window)." Microsoft announced it on February 24, 2025 and now describes it as "fully implemented for tenants in WW environment" (Introducing Exchange Online Tenant Outbound Email Limits).

The formula for standard tenants is 500 × (non-trial email licenses ^ 0.7) + 9,500. Microsoft's sample values:

What matters for cold email:

• New tenants get less. An update of August 13, 2026 applies a reduced quota to newly created tenants, rolling out from September 14, 2026: 10% of the calculated quota for tenants under 31 days old and 25% from 31 to 60 days. A single-license tenant in its first month gets 10% of 10,000, or 1,000 external recipients a day.

• Trial tenants are capped low. The blog says 500 external recipients a day; the Exchange Online limits page says 5,000. Treat a trial tenant as unfit for outreach either way.

• Repeat sends count. "If I send 1,000 messages to the same external recipient in a day," it counts as 1,000.

• Every mailbox shares it. The quota is per tenant, so one heavy sender uses up capacity for everyone.

Mail from the default onmicrosoft.com domain is capped separately at 100 external recipients per organization in a rolling 24 hours, with bounce 550 5.7.236.

High Volume Email Is Not an Option for Outreach

Microsoft's High Volume Email (HVE) has no recipient or message rate limit, but its recipient scope is "Internal recipients within the tenant only" and Microsoft states that "HVE accounts cannot be used for external email delivery" (Manage High Volume Email for Microsoft 365). It does not help with cold email.

Outlook.com Sending Limits

Consumer Outlook.com accounts (outlook.com, hotmail.com, live.com) have their own limits. Microsoft's Outlook.com sending limits page lists them for Microsoft 365 subscribers:

A "non-relationship recipient" is "someone you've never sent email to before," which is every recipient of a cold email. Microsoft notes that limits "will be lower for non-subscribers" and that a new account starts with "a low sending quota" until it establishes credibility.

What Happens When You Hit the Limit

Microsoft's NDR reference for Exchange Online lists the bounces:

For 5.1.90 and 5.2.2 Microsoft adds that the error "could indicate that the account was compromised and is being used to send spam." The quota errors clear when the 24-hour count falls. The ban codes don't: they need an admin and Microsoft support.

Outbound Spam Controls Put the Whole Tenant at Risk

The published limits are not the only ones. Microsoft's outbound spam protection documentation says:

• Accounts that send too much spam are blocked when they exceed "an undisclosed limit," with "different thresholds for individual users and the entire organization."

• Separate limits block accounts "when they reach an overall outbound message limit, regardless the spam filtering verdict."

• Microsoft does not publish these limits "so spammers can't game the system."

• Mail judged as spam leaves from a "high-risk delivery pool" of less reputable IP addresses.

• Microsoft recommends not using "addresses in your primary email domain" as bulk senders, because it "can affect the delivery of regular email from senders in the domain."

So cold email from your company's Microsoft 365 tenant risks more than one mailbox. A ban at tenant level (5.7.705) stops everyone's outbound mail, including sales and support on your main domain.

Platform Limit Is Not a Safe Cold Email Volume

10,000 recipients a day is when Microsoft stops the mailbox, not where your emails land. Outlook filters decide placement far below that.

Our recommendation, whatever the mailbox provider:

• Up to 25 cold emails per mailbox a day, not counting warm-up: 10,000 ÷ 25 = 400 times below the recipient rate limit. See cold emails per mailbox per day.

• Up to 5 mailboxes per domain, and never your main company domain. See main domain for cold email.

• At least 14 days of warm-up before cold email, full volume from around day 21.

• Authenticate every domain. Since May 5, 2025, Outlook.com rejects mail from domains sending more than 5,000 emails a day that fail SPF, DKIM or DMARC, with 550; 5.7.515 Access denied, sending domain [SendingDomain] does not meet the required authentication level (Microsoft Defender for Office 365 blog). The rule covers Outlook.com, "our consumer service, which is supporting hotmail.com live.com and outlook.com consumer domain addresses." Setup details: SPF, DKIM and DMARC for cold email.

If Outlook recipients junk or reject your mail, read the bounce first: why Outlook blocks cold email maps each code to a fix. Google's equivalents are in Google Workspace and Gmail sending limits. To plan mailboxes for a daily target, use the cold email capacity calculator.

FAQ

How many emails can I send per day from Microsoft 365?

Each mailbox can send to 10,000 recipients in a rolling 24 hours, and the tenant has a separate daily cap on external recipients: 10,000 for one license, 12,006 for 10 and 22,059 for 100, lower for new tenants.

What is the Outlook sending limit per minute?

30 messages per minute per mailbox. Over SMTP client submission, messages above that are rejected and the client has to retry.

What does error 5.2.2 "Submission quota exceeded" mean?

The mailbox went over the recipient rate limit or the message rate limit. Sending resumes once the count for the last 24 hours drops below the limit. Microsoft also says it can indicate a compromised account.

Can I raise the Microsoft 365 sending limit?

Admins can change the recipients-per-message limit, from 1 to 1,000. The limits page lists 10,000 recipients a day on every plan and describes no way to raise it. The tenant external cap rises with more email licenses.

Can I use Microsoft 365 for cold email?

Microsoft says Exchange Online isn't suited to bulk mailing, and outbound spam controls can block single users or the entire organization. If you do, keep volume low per mailbox and keep outreach out of the tenant that runs your main domain.

Sources

Checked September 2026:

• Microsoft Learn: Exchange Online limits: recipient rate limit of 10,000 a day, recipient limit customizable up to 1,000, 30 messages per minute, about 200 for encrypted messages, sliding-window example, behavior above the message rate, bulk email note, TERRL definition and 5,000 trial cap, onmicrosoft.com cap of 100 with 550 5.7.236, no per-mailbox external limit listed.

• Exchange Team Blog: Introducing Exchange Online Tenant Outbound Email Limits: TERRL announcement of February 24, 2025, formula and sample values, new-tenant reduction from the August 13, 2026 update, 500 for trial tenants, counting of repeat sends, 5.7.232 and 5.7.233.

• Microsoft Learn: Manage High Volume Email for Microsoft 365: HVE has no recipient or message rate limit, internal recipients only, cannot be used for external delivery.

• Microsoft Support: Sending limits in Outlook.com: 5,000 daily recipients, 500 per message, 1,000 non-relationship recipients, lower for non-subscribers and new accounts.

• Microsoft Learn: Email nondelivery reports and SMTP errors in Exchange Online: texts and causes of 5.1.90, 5.2.2, 5.7.232, 5.7.233, 4.7.500-699, 5.7.501 to 5.7.503 and 5.7.705.

• Microsoft Learn: Outbound spam protection: undisclosed user and organization thresholds, overall outbound limits, high-risk delivery pool, advice against bulk sending from the primary domain.

• Microsoft Defender for Office 365 blog: Outlook's new requirements for high-volume senders: 5,000 emails a day threshold, SPF, DKIM and DMARC requirements, rejection with 550 5.7.515 from May 5, 2025, scope of Outlook.com consumer domains.

Outreach2day mailboxes are standard SMTP/IMAP mailboxes on your own domains, with SPF, DKIM and DMARC set up automatically and warm-up included, at $2.50 per mailbox a month.

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